pwm: meson: Drop always false check from .apply()

The PWM core only calls the apply callback with a valid state pointer,
so don't repeat this check already done in the core.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>