rsa: add sha256,rsa4096 algorithm

Add support for sha256,rsa4096 signatures in u-boot.

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Simon Glass <sjg@chromium.org>
Cc: andreas@oetken.name
diff --git a/include/rsa-checksum.h b/include/rsa-checksum.h
index 850b253..612db85 100644
--- a/include/rsa-checksum.h
+++ b/include/rsa-checksum.h
@@ -12,6 +12,7 @@
 #include <sha1.h>
 #include <sha256.h>
 
+extern const uint8_t padding_sha256_rsa4096[];
 extern const uint8_t padding_sha256_rsa2048[];
 extern const uint8_t padding_sha1_rsa2048[];