pwm: pxa: Add optional reset control

pwm: pxa: Add optional reset control

Support optional reset control for the PWM PXA driver.

During probe, it acquires the reset controller using
devm_reset_control_get_optional_exclusive_deasserted() to get and deassert
the reset controller to enable the PWM channel.

Signed-off-by: Guodong Xu <guodong@riscstar.com>
Link: https://lore.kernel.org/r/20250429085048.1310409-3-guodong@riscstar.com
[ukleinek: Fix conflict with commit df08fff8add2 ("pwm: pxa: Improve using dev_err_probe()")]
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>