pwm: atmel-tcb: Use min() macro

Use the min() macro to simplify the atmel_tcb_pwm_apply() function
and improve its readability.

Signed-off-by: Shen Lichuan <shenlichuan@vivo.com>
Link: https://lore.kernel.org/r/20240827075749.67583-1-shenlichuan@vivo.com


Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>