feat(mbedtls-psa): introduce PSA_CRYPTO build option

This is a preparatory patch to provide MbedTLS PSA Crypto
API support, with below changes -

1. Added a build macro PSA_CRYPTO to enable the MbedTLS PSA
   Crypto API support in the subsequent patches.
2. Compile necessary PSA crypto files from MbedTLS source code
   when PSA_CRYPTO=1.

Also, marked PSA_CRYPTO as an experimental feature.

Change-Id: I45188f56c5c98b169b2e21e365150b1825c6c450
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/drivers/auth/mbedtls/mbedtls_common.mk b/drivers/auth/mbedtls/mbedtls_common.mk
index 79c4512..376b6b7 100644
--- a/drivers/auth/mbedtls/mbedtls_common.mk
+++ b/drivers/auth/mbedtls/mbedtls_common.mk
@@ -23,7 +23,11 @@
 ifeq (${MBEDTLS_MAJOR}, 2)
 	MBEDTLS_CONFIG_FILE	?=	"<drivers/auth/mbedtls/mbedtls_config-2.h>"
 else ifeq (${MBEDTLS_MAJOR}, 3)
-	MBEDTLS_CONFIG_FILE	?=	"<drivers/auth/mbedtls/mbedtls_config-3.h>"
+	ifeq (${PSA_CRYPTO},1)
+		MBEDTLS_CONFIG_FILE     ?=      "<drivers/auth/mbedtls/psa_mbedtls_config.h>"
+	else
+		MBEDTLS_CONFIG_FILE	?=	"<drivers/auth/mbedtls/mbedtls_config-3.h>"
+	endif
 endif
 
 $(eval $(call add_define,MBEDTLS_CONFIG_FILE))
@@ -77,6 +81,18 @@
 	LIBMBEDTLS_CFLAGS += -Wno-error=redundant-decls
 endif
 
+ifeq (${PSA_CRYPTO},1)
+LIBMBEDTLS_SRCS         += $(addprefix ${MBEDTLS_DIR}/library/,    	\
+					psa_crypto.c                   	\
+					psa_crypto_client.c            	\
+					psa_crypto_driver_wrappers.c   	\
+					psa_crypto_hash.c              	\
+					psa_crypto_rsa.c               	\
+					psa_crypto_ecp.c               	\
+					psa_crypto_slot_management.c   	\
+					)
+endif
+
 # The platform may define the variable 'TF_MBEDTLS_KEY_ALG' to select the key
 # algorithm to use. If the variable is not defined, select it based on
 # algorithm used for key generation `KEY_ALG`. If `KEY_ALG` is not defined,