leds: leds-qpnp: Add QPNP PMIC led driver

QPNP (Qualcomm Plug N Play) LEDs driver is used for
controlling LEDs that are part of PMIC on Qualcomm reference
platforms. The PMIC is connected to Host processor via
SPMI bus. This driver supports various LED modules such as
WLED (white LED), RGB LED and flash LED. The first version of
the driver supports WLED and other features are added in the
next versions.

Change-Id: Ib2962c784cf566905f909faa0d46f8ebfee77b2d
Signed-off-by: Amy Maloche <amaloche@codeaurora.org>