lib: crypto: import pkcs7_verify.c from linux

The file, pkcs7_verify.c, will now be imported from linux code
(crypto/asymmetric_keys/pkcs7_verify.c in 5.7) and modified to fit
into U-Boot environment.

In particular, pkcs7_verify_one() function will be used in a later patch
to rework signature verification logic aiming to support intermediate
certificates in "chain of trust."

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index 8267fee..f3a4145 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -44,6 +44,7 @@
 pkcs7_message-y := \
 	pkcs7.asn1.o \
 	pkcs7_parser.o
+obj-$(CONFIG_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