test: add rsa_verify() unit test

In this patch, a very simple test is added to verify that rsa_verify()
using rsa_verify_with_pkey() work correctly.

To keep the code simple, all the test data, either public key and
verified binary data, are embedded in the source.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
diff --git a/test/Kconfig b/test/Kconfig
index cb51b46..0157e0b 100644
--- a/test/Kconfig
+++ b/test/Kconfig
@@ -28,6 +28,16 @@
 	  Enables a test which exercises asn1 compiler and decoder function
 	  via various parsers.
 
+config UT_LIB_RSA
+	bool "Unit test for rsa_verify() function"
+	depends on RSA
+	depends on RSA_VERIFY_WITH_PKEY
+	select IMAGE_SIGN_INFO
+	default y
+	help
+	  Enables rsa_verify() test, currently rsa_verify_with_pkey only()
+	  only, at the 'ut lib' command.
+
 endif
 
 config UT_TIME