pwm: samsung: do not set manual update bit in pwm_samsung_config

pwm_samsung_config() sets the manual update bit via a call to the
pwm_samsung_enable() function even when the channel is already running.
This causes noticable flicker on display if we try to change the
backlight brightness from minimum to maximum, continuously.

So, we remove the call to pwm_samsung_enable() from pwm_samsung_config
to avoid the flicker and this change doesn't harm normal working since
the pwm-backlight driver already calls pwm_samsung_enable() where
needed.

Signed-off-by: Ajay Kumar <ajaykumar.rs@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>