pwm: qpnp: correct LUT mode LPG disable steps

Modify the pwm-qpnp driver in order to remove RAMP_CONTROL
register writes during LPG disable while in LUT mode.

This is needed to fix the LED blink functionality
when LPG enable/disable operations are performed continously

CRs-Fixed: 593837
Change-Id: I915eb7620902911ef8d3f8d44c9b75986bc69bd1
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>