efikamx: add leds support

The efika mx a 3 leds (1 blue, 1 red, 1 green) connected on GPIOS 3 13/14/15.
Also, some special care is done for default trigger of blue led for mmc as
the mmc host used is different between hw revisions

Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>