tty: serial: fsl_lpuart: Fix the wrong RXWATER setting for rx dma case

The RXWATER value must be greater than 0 according to the LPUART
reference manual. And when the number of datawords in the receive
FIFO is greater than RXWATER, an interrupt or a DMA request is
generated, so no need to set the different value for lpuart interrupt
case and dma case. Here delete the wrong RXWATER setting for dma case
directly.

Fixes: 42b68768 ("serial: fsl_lpuart: DMA support for 32-bit variant")
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Link: https://lore.kernel.org/r/20230130064449.9564-4-sherry.sun@nxp.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -1729,12 +1729,6 @@ static void lpuart32_configure(struct lpuart_port *sport)
 {
 	unsigned long temp;
 
-	if (sport->lpuart_dma_rx_use) {
-		/* RXWATER must be 0 */
-		temp = lpuart32_read(&sport->port, UARTWATER);
-		temp &= ~(UARTWATER_WATER_MASK << UARTWATER_RXWATER_OFF);
-		lpuart32_write(&sport->port, temp, UARTWATER);
-	}
 	temp = lpuart32_read(&sport->port, UARTCTRL);
 	if (!sport->lpuart_dma_rx_use)
 		temp |= UARTCTRL_RIE | UARTCTRL_ILIE;