lib: Rename rsa-checksum.c to hash-checksum.c

rsa-checksum.c sontains the hash_calculate() implementations. Despite
the "rsa-" file prefix, this function is useful for other algorithms.

To prevent confusion, move this file to lib/, and rename it to
hash-checksum.c, to give it a more "generic" feel.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/image.h

@@ -1283,7 +1283,7 @@ struct image_region {
 };
 
 #if IMAGE_ENABLE_VERIFY
-# include <u-boot/rsa-checksum.h>
+# include <u-boot/hash-checksum.h>
 #endif
 struct checksum_algo {
 	const char *name;