Three bugs have been fixed in this commit:
1. When the duty was set with duty_u16(), changing the freq with pwm.freq()
would not keep relative duty rate, but the absolute pulse duration.
2. Fix another inconsistency when displaying the PWM pin's properties of a
QTMR channel.
3. Improve the error checks for the second channel being a PWM pin and pin
pairs to be a FLEXPWM A/B pair.
Signed-off-by: robert-hh <robert@hammelrath.com>
8f6315a279