asn1_decoder: add build options for ASN1 decoder

When building with MbedTLS, we are using MbedTLS to decode ASN1 data
for x509, pkcs7 and mscode.
Introduce _LEGACY and _MBEDTLS kconfigs for ASN1 decoder legacy and
MbedTLS implementations respectively.

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/lib/mbedtls/Kconfig b/lib/mbedtls/Kconfig
index ab50ad4..d71adc3 100644
--- a/lib/mbedtls/Kconfig
+++ b/lib/mbedtls/Kconfig
@@ -116,12 +116,14 @@
 
 config LEGACY_CRYPTO_CERT
 	bool "legacy certificate libraries"
+	select ASN1_DECODER_LEGACY if ASN1_DECODER
 	select ASYMMETRIC_PUBLIC_KEY_LEGACY if \
 		ASYMMETRIC_PUBLIC_KEY_SUBTYPE
 	select RSA_PUBLIC_KEY_PARSER_LEGACY if RSA_PUBLIC_KEY_PARSER
 	select X509_CERTIFICATE_PARSER_LEGACY if X509_CERTIFICATE_PARSER
 	select PKCS7_MESSAGE_PARSER_LEGACY if PKCS7_MESSAGE_PARSER
 	select MSCODE_PARSER_LEGACY if MSCODE_PARSER
+	select SPL_ASN1_DECODER_LEGACY if SPL_ASN1_DECODER
 	select SPL_ASYMMETRIC_PUBLIC_KEY_LEGACY if \
 		SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
 	select SPL_RSA_PUBLIC_KEY_PARSER_LEGACY if SPL_RSA_PUBLIC_KEY_PARSER
@@ -130,6 +132,12 @@
 
 if LEGACY_CRYPTO_CERT
 
+config ASN1_DECODER_LEGACY
+	bool "ASN1 decoder with legacy certificate library"
+	depends on LEGACY_CRYPTO_CERT && ASN1_DECODER
+	help
+	  This option chooses legacy certificate library for ASN1 decoder.
+
 config ASYMMETRIC_PUBLIC_KEY_LEGACY
 	bool "Asymmetric public key crypto with legacy certificate library"
 	depends on LEGACY_CRYPTO_CERT && ASYMMETRIC_PUBLIC_KEY_SUBTYPE
@@ -171,6 +179,13 @@
 
 if SPL
 
+config SPL_ASN1_DECODER_LEGACY
+	bool "ASN1 decoder with legacy certificate library in SPL"
+	depends on LEGACY_CRYPTO_CERT && SPL_ASN1_DECODER
+	help
+	  This option chooses legacy certificate library for ASN1 decoder in
+	  SPL.
+
 config SPL_ASYMMETRIC_PUBLIC_KEY_LEGACY
 	bool "Asymmetric public key crypto with legacy certificate library in SPL"
 	depends on LEGACY_CRYPTO_CERT && SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
@@ -326,12 +341,14 @@
 
 config MBEDTLS_LIB_X509
 	bool "MbedTLS certificate libraries"
+	select ASN1_DECODER_MBEDTLS if ASN1_DECODER
 	select ASYMMETRIC_PUBLIC_KEY_MBEDTLS if \
 		ASYMMETRIC_PUBLIC_KEY_SUBTYPE
 	select RSA_PUBLIC_KEY_PARSER_MBEDTLS if RSA_PUBLIC_KEY_PARSER
 	select X509_CERTIFICATE_PARSER_MBEDTLS if X509_CERTIFICATE_PARSER
 	select PKCS7_MESSAGE_PARSER_MBEDTLS if PKCS7_MESSAGE_PARSER
 	select MSCODE_PARSER_MBEDTLS if MSCODE_PARSER
+	select SPL_ASN1_DECODER_MBEDTLS if SPL_ASN1_DECODER
 	select SPL_ASYMMETRIC_PUBLIC_KEY_MBEDTLS if \
 		SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE
 	select SPL_RSA_PUBLIC_KEY_PARSER_MBEDTLS if SPL_RSA_PUBLIC_KEY_PARSER
@@ -340,6 +357,12 @@
 
 if MBEDTLS_LIB_X509
 
+config ASN1_DECODER_MBEDTLS
+	bool "ASN1 decoder with MbedTLS certificate library"
+	depends on MBEDTLS_LIB_X509 && ASN1_DECODER
+	help
+	  This option chooses MbedTLS certificate library for ASN1 decoder.
+
 config ASYMMETRIC_PUBLIC_KEY_MBEDTLS
 	bool "Asymmetric public key crypto with MbedTLS certificate library"
 	depends on MBEDTLS_LIB_X509 && ASYMMETRIC_PUBLIC_KEY_SUBTYPE
@@ -381,6 +404,13 @@
 
 if SPL
 
+config SPL_ASN1_DECODER_MBEDTLS
+	bool "ASN1 decoder with MbedTLS certificate library in SPL"
+	depends on MBEDTLS_LIB_X509 && SPL_ASN1_DECODER
+	help
+	  This option chooses MbedTLS certificate library for ASN1 decoder in
+	  SPL.
+
 config SPL_ASYMMETRIC_PUBLIC_KEY_MBEDTLS
 	bool "Asymmetric public key crypto with MbedTLS certificate library in SPL"
 	depends on MBEDTLS_LIB_X509 && SPL_ASYMMETRIC_PUBLIC_KEY_SUBTYPE