pwm: meson: fix handling of period/duty if greater than UINT_MAX

state->period/duty are of type u64, and if their value is greater than
UINT_MAX, then the cast to uint will cause problems. Fix this by
changing the type of the respective local variables to u64.

Fixes: b79c3670 ("pwm: meson: Don't duplicate the polarity internally")
Cc: stable@vger.kernel.org
Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>