drivers: emios_pwm: do not configure period, duty and polarity at boot

Removing period, duty and polarity configuration from
channel devicetree. At boot time, only minimal setup like
pinctrl, prescaler, etc should be initialized. PWM signal
is produced by using pwm_set* API

Also after this change, PWM period, duty are changed at the
next counter period boundary

Signed-off-by: Dat Nguyen Duy <dat.nguyenduy@nxp.com>