serial: Add auart driver for i.MX23/28

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index 8ea92e9..c855071 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -92,3 +92,4 @@
 obj-$(CONFIG_SERIAL_MFD_HSU)	+= mfd.o
 obj-$(CONFIG_SERIAL_IFX6X60)  	+= ifx6x60.o
 obj-$(CONFIG_SERIAL_PCH_UART)	+= pch_uart.o
+obj-$(CONFIG_SERIAL_MXS_AUART) += mxs-auart.o