boards: nucleo_l476rg and nucleo_wb55rg add timers

nucleo_l476rg:
adds tim3 with pwm on pb4, changes tim2 pwm pin from pa0 to pb10.
As a result timers are available on arduino pins D5 and D6.

nucleo_wb55rg:
adds tim1 with pwm on pa8, changes tim2 pwm pin from pa0 to pa15.
As a result timers are available on arduino pins D5 and D6.

Use default prescaler (==1) for 32-bit timer and
10.001 for 16-bit timers, as these are commonly used.

Signed-off-by: Thomas Stranger <thomas.stranger@outlook.com>