pwm: nrf5_sw: do not use 'inversed' polarity by default
pwm: nrf5_sw: do not use 'inversed' polarity by default

The default PWM polarity was 'inversed', which is not aligned with the
other PWM drivers. Unfortunately there is not yet an API to define the
default polarity to be used by the driver, but assume that 'normal'
(signal starts high for the duration of the duty cycle) should be the
default.

Signed-off-by: Ricardo Salveti <d4e7430f1534a12df46cedd1ac369935436dbb94@opensourcefoundries.com>

explora26/zephyr,punitvara/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,zephyriot/zephyr,galak/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,mbolivar/zephyr,Vudentz/zephyr,ldts/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,Vudentz/zephyr,galak/zephyr,kraj/zephyr,explora26/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,nashif/zephyr,explora26/zephyr,ldts/zephyr,ldts/zephyr,mbolivar/zephyr,kraj/zephyr,finikorg/zephyr,punitvara/zephyr,punitvara/zephyr,Vudentz/zephyr,mbolivar/zephyr,zephyriot/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,kraj/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,punitvara/zephyr,mbolivar/zephyr,GiulianoFranchetto/zephyr,mbolivar/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,explora26/zephyr,zephyriot/zephyr,nashif/zephyr,finikorg/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr