pwm: samsung: Don't uses devm_*() functions in ->request()

A call to ->request() is always paired by a call to ->free() before a
given device is disposed. So the simplification that usually is possible
when using devm_*() functions cannot be used here. So use plain
kzalloc() and kfree() for improved runtime behaviour and reduced memory
footprint.

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