mbed: fix crash on digital* operations

[facchinm]

Fix functionality (and the infamous blink of death) on mbed enabled boards.

Tested on Nano RP2040 Connect and Portenta H7 (should work on all supported boards

@gbr1

[sebromero]

@facchinm FYI Does not work yet on Arduino Nicla Vision and Arduino Nicla Sense ME.

[gbr1]

@sebromero @facchinm it seems to still create issues using threads :'(

[sebromero]

@gbr1 can you elaborate? What issues?

[gbr1]

@sebromero if you use the OneWire class and/or methods inside a thread it doens't work and it causes the immediate thread kill. Probably there is something that locks interrupts or similar