boards: nucleo_g0b1 add timers, move spi2, nucleo_g474, add timers

nucleo_g0b1re:
removes spi2 from arduino header pins to ST morpho pins in order to
free pins for other peripherals.
Adds tim15 with pwm on pb14, changes tim3 pwm to pb4.
As a result timers are available on arduino pins D5 and D6.

nucleo g474re:
Adds timer 3 with pwm  pin on pb4 and changes tim2 pwm pin
from pa5 to pb10.
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>