sweep2wake: enable dynamic button_backlight

If the screen is offline and you touch the home button (aka start a
sweep2unlock) the capacitive buttons will light up to guide your path.
They will be shutdown again as soon as you lift your finger.

Conflicts:

	drivers/input/touchscreen/cy8c_tma_ts.c
	drivers/leds/leds-pm8058.c
	include/linux/cy8c_tma_ts.h