pwm: ep93xx: Ensure configuring period and duty_cycle isn't wrongly skipped

As the last call to ep93xx_pwm_apply() might have exited early if
state->enabled was false, the values for period and duty_cycle stored in
pwm->state might not have been written to hardware and it must be
ensured that they are configured before enabling the PWM.

Fixes: 6d45374a ("pwm: ep93xx: Implement .apply callback")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>