arm: socfpga: mailbox: Always read mailbox responses before returning status

Mailbox driver should always check for the length of the response
and read the response data before returning the response status to
caller.
Signed-off-by: NChee Hong Ang <chee.hong.ang@intel.com>
Reviewed-by: NLey Foon Tan <ley.foon.tan@intel.com>

arch/arm/mach-socfpga/mailbox_s10.c

@@ -221,9 +221,7 @@ static __always_inline int mbox_send_cmd_common(u8 id, u32 cmd, u8 is_indirect,
 			if ((MBOX_RESP_CLIENT_GET(resp) ==
 			     MBOX_CLIENT_ID_UBOOT) &&
 			    (MBOX_RESP_ID_GET(resp) == id)) {
-				ret = MBOX_RESP_ERR_GET(resp);
-				if (ret)
-					return ret;
+				int resp_err = MBOX_RESP_ERR_GET(resp);
 
 				if (resp_buf_len) {
 					buf_len = *resp_buf_len;
@@ -252,7 +250,7 @@ static __always_inline int mbox_send_cmd_common(u8 id, u32 cmd, u8 is_indirect,
 						buf_len--;
 					}
 				}
-				return ret;
+				return resp_err;
 			}
 		}
 	};