qpnp: pwm: PM8110 pwm changes for backlight

Qualcomm pmic chipset PM8110's ENABLE_CONTROL register
definition is different from other pmic chipset. So avoid
modifying the other bits in ENABLE_CONTROL register when
pwm_config is called.

CRs-Fixed: 502742
Change-Id: Ib0b237c44dcc359536879c506e32dc945b47a0b8
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>