Input: mcs5000_ts - protect PM functions with CONFIG_PM_SLEEP

Input: mcs5000_ts - protect PM functions with CONFIG_PM_SLEEP

When a kernel has CONFIG_PM=y and CONFIG_PM_SLEEP=n the following warnings are
seen:
drivers/input/touchscreen/mcs5000_ts.c:252:12: warning: 'mcs5000_ts_suspend' defined but not used [-Wunused-function]
 static int mcs5000_ts_suspend(struct device *dev)
            ^
drivers/input/touchscreen/mcs5000_ts.c:262:12: warning: 'mcs5000_ts_resume' defined but not used [-Wunused-function]
 static int mcs5000_ts_resume(struct device *dev)

Protect the suspend/resume functions with CONFIG_PM_SLEEP in order to fix these
build warnings.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>