serial: omap: Support debug UART

Add debug UART functions to permit omap specific ns16550 to
provide an early debug UART. This is mostly in common with
DEBUG_UART_NS16550 except for Mode definition register which
is required for selecting UART mode(16x auto-baud or 13x mode).

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 7249945..58fc7cd 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -257,6 +257,13 @@
 	  driver will be available until the real driver-model serial is
 	  running.
 
+config DEBUG_UART_OMAP
+	bool "OMAP uart"
+	help
+	  Select this to enable a debug UART using the omap ns16550 driver.
+	  You will need to provide parameters to make this work. The driver
+	  will be available until the real driver model serial is running.
+
 endchoice
 
 config DEBUG_UART_BASE