ARM: dts: Enable N950 keyboard sleep leds by default

Like the Nokia N900, the N950 has leds to show
the state of sys_clkreq and sys_off_mode pins.

A detailed description for the LEDs and
OMAP's sleep states can be found in Tony's
commit for the Nokia N900:

c1be2032

Signed-off-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>