serial: fsl_lpuart: don't modify arbitrary data on lpuart32

lpuart_rx_dma_startup() is used for both the 8 bit and the 32 bit
version of the LPUART. Modify the UARTCR only for the 8 bit version.

Fixes: f4eef224 ("serial: fsl_lpuart: add sysrq support when using dma")
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20210512141255.18277-2-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -1625,7 +1625,7 @@ static void lpuart_rx_dma_startup(struct lpuart_port *sport)
 	sport->lpuart_dma_rx_use = true;
 	rx_dma_timer_init(sport);
 
-	if (sport->port.has_sysrq) {
+	if (sport->port.has_sysrq && !lpuart_is_32(sport)) {
 		cr3 = readb(sport->port.membase + UARTCR3);
 		cr3 |= UARTCR3_FEIE;
 		writeb(cr3, sport->port.membase + UARTCR3);