Update Armada 38x UART device tree binding

Recent changes in Linux updated Marvell Armada 38x
UART compatible string. As a result the FreeBSD driver
(uart_dev_snps) does not probe. This commit fixes the
situation, however not applying any functional modification
to the driver methods.

Approved by: re (kib)
Obtained from: Semihalf

sys/dev/uart/uart_dev_snps.c

@@ -127,6 +127,7 @@ struct uart_class uart_snps_class = {
 
 static struct ofw_compat_data compat_data[] = {
 	{ "snps,dw-apb-uart",		(uintptr_t)&uart_snps_class },
+	{ "marvell,armada-38x-uart",	(uintptr_t)&uart_snps_class },
 	{ NULL,				(uintptr_t)NULL }
 };
 UART_FDT_CLASS(compat_data);