serial: ns16550: Add Intel XScale support

Add compatible string for the Intel XScale variant of the 16550. Needed
to match upstream.

Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
index 039da83..0e267d0 100644
--- a/drivers/serial/ns16550.c
+++ b/drivers/serial/ns16550.c
@@ -605,6 +605,7 @@
 	{ .compatible = "ingenic,jz4780-uart",	.data = PORT_JZ4780  },
 	{ .compatible = "nvidia,tegra20-uart",	.data = PORT_NS16550 },
 	{ .compatible = "snps,dw-apb-uart",	.data = PORT_NS16550 },
+	{ .compatible = "intel,xscale-uart",	.data = PORT_NS16550 },
 	{}
 };
 #endif /* OF_REAL */