mdss: display: remove the pwm gpio request from edp backlight

There is no use of the pwm gpio inside the driver so cleaning up the code
and removing it from devicetree.

Change-Id: I72c038f3082aa6ed18ea9142de75faecc1e1e0fd
Signed-off-by: Asaf Penso <apenso@codeaurora.org>
mdss:display: add regulator control to dsi-1

Regulators are shared by both dsi controller. For both
dual and split display application regulator should be
controlled individually to avoid reualtors are turned off
while dsi-1 still running which cause DLB0_ERR_CONTENTION_LP1
error.

CRs-fixed: 579900
Change-Id: Ia29bd3e49a405ccb1ad55f08f3897cee2ff6f4c6
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>