pwm: qpnp: configure PWM period during bootup

Currently, PWM period is configured only when the client request
to configure period explicitly. However, there are requirements
to get it configured during bootup based upon the device tree
configuration. Add support for it.

While at it, add some pr_debug statements to the driver so that
it can provide some useful log of PWM specific calculations
runtime.

CRs-Fixed: 984628
Change-Id: I50de4488c32ef78efec1587305c56ab06fb32fed
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>