lib: ecdsa: Implement UCLASS_ECDSA verification on target

Implement the crypto_algo .verify() function for ecdsa256. Because
it backends on UCLASS_ECDSA, this change is focused on parsing the
keys from devicetree and passing this information to the specific
UCLASS driver.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/lib/Kconfig b/lib/Kconfig
index 7b445d0..c535147 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -303,6 +303,7 @@
 	  supported by the algorithm but only a 128-bit key is supported at
 	  present.
 
+source lib/ecdsa/Kconfig
 source lib/rsa/Kconfig
 source lib/crypto/Kconfig
 source lib/crypt/Kconfig