From: Olliver Schinagl <oliver@schinagl.nl>
This patch adds a bit-banging gpio PWM driver. It makes use of hrtimers,
to allow nano-second resolution, though it obviously strongly depends on
the switching speed of the gpio pins, hrtimer and system load.
Each pwm node can have 1 or more "pwm-gpio" entries, which will be
treated as pwm's as part of a pwm chip.
Change-Id: Idd42bf6d79f8ce52275a15965b02af470f28da7c
Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>