pwm: samsung: Remove redundant checks from pwm_samsung_config()

If the requested period_ns and duty_ns values are identical to the last
programmed ones pwm_samsung_config() returns early and skips the
hardware configuration. The same checks are now done by the PWM core so
the driver specific ones can be removed.

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>