mfd: rave-sp: Check received frame length before accepting next byte

Check received frame length _before_ accepting next byte in order to
avoid incorrectly rejecting payloads that are RAVE_SP_RX_BUFFER_SIZE
long.
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Tested-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/rave-sp.c

@@ -546,8 +546,6 @@ static int rave_sp_receive_buf(struct serdev_device *serdev,
 			/* FALLTHROUGH */
 
 		case RAVE_SP_EXPECT_ESCAPED_DATA:
-			deframer->data[deframer->length++] = byte;
-
 			if (deframer->length == sizeof(deframer->data)) {
 				dev_warn(dev, "Bad frame: Too long\n");
 				/*
@@ -562,6 +560,8 @@ static int rave_sp_receive_buf(struct serdev_device *serdev,
 				goto reset_framer;
 			}
 
+			deframer->data[deframer->length++] = byte;
+
 			/*
 			 * We've extracted out special byte, now we
 			 * can go back to regular data collecting