mfd: pm8xxx-pwm: Add software workaround to cover PM8038 hardware bug

In PM8038 PMIC chipset, there is a hardware bug in the PWM module
design so that if a PWM write results in input of logic 0 followed
by a pwm_en = 0 then the subsequent write of PWM value will not be
updated to the output.

Add an additional PWM write before enabling PWM so that PWM value
is updated at the output.

CRs-fixed: 386451
Change-Id: Id09ad7084936d7b7922ceaae24006f879f19454c
Signed-off-by: Jay Chokshi <jchokshi@codeaurora.org>