pwm: Drop pwm_apply_state()

This function is not supposed to be used any more since commit
c748a6d7 ("pwm: Rename pwm_apply_state() to
pwm_apply_might_sleep()") that is included in v6.8-rc1. Two kernel
releases should be enough for everyone to adapt, so drop the old
function that was introduced as a compatibility stub for the transition.

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