drivers: pwm: stm32: support capturing on four channels

Previously the pwm capture only support capturing on channel 1
and 2, because the slave mode controller was used, which uses
the signal TIxFP which is not available for channel 3 and 4.

This commit adds optional support for four channel capturing by
changing the method of capturing PWM signals to not use the
slave mode controller to reset the counter register. Instead the
counter is reset in the ISR. This will result in a slight loss
of accuracy but is still within an acceptable range.

Co-authored-by: Jeroen van Dooren <jeroen.van.dooren@nobleo.nl>
Signed-off-by: Hein Wessels <heinwessels93@gmail.com>