crypto: img-hash - Fix hash request context

Move 0 length buffer to end of structure to stop overwriting
fallback request data. This doesn't cause a bug itself as the
buffer is never used alongside the fallback but should be
changed.
Signed-off-by: NWill Thomas <will.thomas@imgtec.com>
Reviewed-by: NJames Hartley <james.hartley@imgtec.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/img-hash.c

@@ -102,8 +102,10 @@ struct img_hash_request_ctx {
 	unsigned long		op;
 
 	size_t			bufcnt;
-	u8 buffer[0] __aligned(sizeof(u32));
 	struct ahash_request	fallback_req;
+
+	/* Zero length buffer must remain last member of struct */
+	u8 buffer[0] __aligned(sizeof(u32));
 };
 
 struct img_hash_ctx {