lib/crypto: Adapt PKCS7 parser to MbedTLS

Previous patch has introduced MbedTLS porting layer for PKCS7 parser,
here to adjust the header and makefiles accordingly.

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index 4302f19..7129315 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -50,15 +50,16 @@
 # PKCS#7 message handling
 #
 obj-$(CONFIG_$(SPL_)PKCS7_MESSAGE_PARSER) += pkcs7_message.o
-pkcs7_message-y := \
+pkcs7_message-y := pkcs7_helper.o
+pkcs7_message-$(CONFIG_$(SPL_)PKCS7_MESSAGE_PARSER_LEGACY) += \
 	pkcs7.asn1.o \
-	pkcs7_helper.o \
 	pkcs7_parser.o
-obj-$(CONFIG_$(SPL_)PKCS7_VERIFY) += pkcs7_verify.o
 
 $(obj)/pkcs7_parser.o: $(obj)/pkcs7.asn1.h
 $(obj)/pkcs7.asn1.o: $(obj)/pkcs7.asn1.c $(obj)/pkcs7.asn1.h
 
+obj-$(CONFIG_$(SPL_)PKCS7_VERIFY) += pkcs7_verify.o
+
 #
 # Signed PE binary-wrapped key handling
 #