serial: fsl_lpuart: use UARTDATA_MASK macro

Use the corresponding macro instead of the magic number. While at it,
drop the useless cast to "unsigned char".
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20210512141255.18277-3-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -928,9 +928,9 @@ static void lpuart32_rxint(struct lpuart_port *sport)
 		 */
 		sr = lpuart32_read(&sport->port, UARTSTAT);
 		rx = lpuart32_read(&sport->port, UARTDATA);
-		rx &= 0x3ff;
+		rx &= UARTDATA_MASK;
 
-		if (uart_handle_sysrq_char(&sport->port, (unsigned char)rx))
+		if (uart_handle_sysrq_char(&sport->port, rx))
 			continue;
 
 		if (sr & (UARTSTAT_PE | UARTSTAT_OR | UARTSTAT_FE)) {