leds: leds-qpnp: replace pwm_free with pwm_disable

pwm_free() is called in the driver incorrectly when trying to disable PWM
channel while changing the configuration. pwm_free() checks PWMF_REQUESTED
flag before calling disable() hook. The driver doesn't call pwm_request()
but only calls of_pwm_get() at the probe to get the flag once. The Flag
will be cleared when pwm_free() is called for the first time and calling it
afterwards will simply bailout not calling disable().

Replace pwm_free() with pwm_disable(), this won't cause any issue because
the PWM channel is considered statically allocated to the led devices from
hardware perspective and no need to free it in the driver.

While at it, free the PWM device if any errors when getting PWM
configuration.

CRs-Fixed: 2014600
Change-Id: I373d2a1ac83232ce94933c287b4ebe3f23519c83
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>