lib: crypto: add rsa public key parser

Imported from linux kernel v5.3:
rsapubkey.asn1 without changes
rsa.h without changes
rsa_helper.c with changes marked as __UBOOT__

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index a284de9..69330a9 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -8,3 +8,14 @@
 asymmetric_keys-y := asymmetric_type.o
 
 obj-$(CONFIG_ASYMMETRIC_PUBLIC_KEY_SUBTYPE) += public_key.o
+
+#
+# RSA public key parser
+#
+obj-$(CONFIG_RSA_PUBLIC_KEY_PARSER) += rsa_public_key.o
+rsa_public_key-y := \
+	rsapubkey.asn1.o \
+	rsa_helper.o
+
+$(obj)/rsapubkey.asn1.o: $(obj)/rsapubkey.asn1.c $(obj)/rsapubkey.asn1.h
+$(obj)/rsa_helper.o: $(obj)/rsapubkey.asn1.h