serial: omap: Introduce DM specific omap serial

Add driver model support for OMAP_SERIAL while reusing
the functions in ns16550.c

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Tested-by: Derald D. Woods <woods.technical@gmail.com>
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index 9fa81d8..03dc29e 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -65,6 +65,7 @@
 obj-$(CONFIG_MPC8XX_CONS) += serial_mpc8xx.o
 obj-$(CONFIG_NULLDEV_SERIAL) += serial_nulldev.o
 obj-$(CONFIG_OWL_SERIAL) += serial_owl.o
+obj-$(CONFIG_OMAP_SERIAL) += serial_omap.o
 
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o