lib/crypto: Adapt mscode_parser to MbedTLS

Previous patch has introduced MbedTLS porting layer for mscode parser,
here to adjust the header and makefiles accordingly.
Adding _LEGACY Kconfig for legacy mscode implementation.

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index 7129315..3caa45d 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -63,7 +63,7 @@
 #
 # Signed PE binary-wrapped key handling
 #
-obj-$(CONFIG_$(SPL_)MSCODE_PARSER) += mscode.o
+obj-$(CONFIG_$(SPL_)MSCODE_PARSER_LEGACY) += mscode.o
 
 mscode-y := \
 	mscode_parser.o \