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.h b/include/rsa.h
index e9ae870..a5680ab 100644
--- a/include/rsa.h
+++ b/include/rsa.h
@@ -103,4 +103,14 @@
 }
 #endif
 
+#define RSA2048_BYTES	(2048 / 8)
+#define RSA4096_BYTES	(4096 / 8)
+
+/* This is the minimum/maximum key size we support, in bits */
+#define RSA_MIN_KEY_BITS	2048
+#define RSA_MAX_KEY_BITS	4096
+
+/* This is the maximum signature length that we support, in bits */
+#define RSA_MAX_SIG_BITS	4096
+
 #endif