pwm: qpnp: modify to use pwm_config_us() for some qcom drivers

Kernel 3.10 defines pwm_config() to use nanosecond parameters, but
now some qcom drivers still use pwm_config() to pass microsecond
parameters. pwm-qpnp driver has already provided a new API called
pwm_config_us() to support microsecond parameters, so we should
modify to use pwm_config_us() instead of pwm_config() for these
drivers.

CRs-Fixed: 587715
Change-Id: I222440bb7636972b9ae35eba175ddffc58095ce8
Signed-off-by: Xu Kai <kaixu@codeaurora.org>