serial: imx: remove a redundant check

cpp_check reports
drivers/tty/serial/imx.c:1207:15: style: Condition 'r_bytes>0' is always true [knownConditionTrueFalse]
  if (r_bytes > 0) {

r_byte is set to
  r_bytes = rx_ring->head - rx_ring->tail;

The head - tail calculation is also done by the earlier check
  if (rx_ring->head <= sg_dma_len(sgl) &&
      rx_ring->head > rx_ring->tail) {

so r_bytes will always be > 0, so the second check is not needed.

Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Link: https://lore.kernel.org/r/20230211154550.2130670-1-trix@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Tom Rix

drivers/tty/serial/imx.c

@@ -1204,11 +1204,9 @@ static void imx_uart_dma_rx_callback(void *data)
 		r_bytes = rx_ring->head - rx_ring->tail;
 
 		/* If we received something, check for 0xff flood */
-		if (r_bytes > 0) {
-			spin_lock(&sport->port.lock);
-			imx_uart_check_flood(sport, imx_uart_readl(sport, USR2));
-			spin_unlock(&sport->port.lock);
-		}
+		spin_lock(&sport->port.lock);
+		imx_uart_check_flood(sport, imx_uart_readl(sport, USR2));
+		spin_unlock(&sport->port.lock);
 
 		if (!(sport->port.ignore_status_mask & URXD_DUMMY_READ)) {