lib/crypto: Adapt public_key header with MbedTLS

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

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index 1605908..7e87721 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -7,9 +7,8 @@
 
 asymmetric_keys-y := asymmetric_type.o
 
-obj-$(CONFIG_$(SPL_)ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += \
-	public_key_helper.o \
-	public_key.o
+obj-$(CONFIG_$(SPL_)ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += public_key_helper.o
+obj-$(CONFIG_$(SPL_)ASYMMETRIC_PUBLIC_KEY_LEGACY) += public_key.o
 
 #
 # RSA public key parser