drivers: adc: stm32: fix f3x series

The patch fixes driver compile errors and ADC management for the f3x
series. It was developed and tested for the stm32f373 variant.

Tested-by: Dario Binacchi <dariobin@libero.it>
Signed-off-by: Dario Binacchi <dariobin@libero.it>
1 file changed