ARM: dts: msm: configure PMA8084 GPIO 8 for PWM output on msmsamarium CDP

Specify initial configuration values for PMA8084 GPIO 8 which
connect it to the LPG channel 4 PWM device.  This GPIO is
connected on the msmsamarium CDP board to a backlight LED
driver chip.

Change-Id: I3fb5a6f916d1272147d55e9b481d5f77ba3a5208
Signed-off-by: David Collins <collinsd@codeaurora.org>