serial: xilinx_uartps: kill CONFIG_OF conditional

The Zynq platform requires the use of CONFIG_OF.  Remove the #ifdef
conditionals in the uartps driver.  Make dependency explicit in Kconfig.

Signed-off-by: Josh Cartwright <josh.cartwright@ni.com>
Tested-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index b176801..6a69c88 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1376,6 +1376,7 @@
 
 config SERIAL_XILINX_PS_UART
 	tristate "Xilinx PS UART support"
+	depends on OF
 	select SERIAL_CORE
 	help
 	  This driver supports the Xilinx PS UART port.