leds: Convert mc13783 driver to mc13xxx MFD

mc13xxx is the more general API and most of the mc13783_... functions
are going to die.

Signed-off-by: David Jander <david@protonic.nl>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>