pwm: Drop irrelevant error path from pwmchip_remove()

Since the PWM core uses device links (commit b2c200e3 ("pwm: Add
consumer device link")) each consumer driver that requested the PWMs is
already gone. If they called pwm_put() (as they should) the
PWMF_REQUESTED bit is not set. If they failed (which is a bug) the
PWMF_REQUESTED bit might still be set, but the driver that cared is
gone, so nothing bad happens if the PWM chip goes away even if the
PWMF_REQUESTED is still present.

So the check can be dropped.

With this change pwmchip_remove() returns always 0, so lowlevel drivers
don't need to check the return code any more. Once all drivers dropped
this check this function can be changed to return void.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>