input: xilinx_ps2: Add missing of_address.h header

Add missing header.

Error log:
CC      drivers/input/serio/xilinx_ps2.o
drivers/input/serio/xilinx_ps2.c: In function 'xps2_of_probe':
drivers/input/serio/xilinx_ps2.c:249: error: implicit declaration of function 'of_address_to_resource'
Signed-off-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/input/serio/xilinx_ps2.c

@@ -23,7 +23,7 @@
 #include <linux/init.h>
 #include <linux/list.h>
 #include <linux/io.h>
-
+#include <linux/of_address.h>
 #include <linux/of_device.h>
 #include <linux/of_platform.h>