add pin def for BAT

[sajattack]

Fixes #1149

[tannewt]

Thanks for this PR!

I know BAT is sometimes on the silkscreen but I'd prefer BATTERY. Truncations like BAT are much more difficult for non-native english speakers to understand/look up.

[dhalbert]

Build errors on itsy_bitsy_m4_express: https://travis-ci.org/adafruit/circuitpython/jobs/441508064#L1143

[sajattack]

Ok. I looked at the schematic and it looks like PB01 was the correct pin connected to the BAT pin. Do I have to define it somehow?

[dhalbert]

@sajattack That schematic is for the Feather M4, which uses the 64-pin SAMD51J19. The Itsy Bitsy uses the 48-pin SAMD51G19. I don't see any voltag monitoring stuff on the Itsy M4. Schematic here: https://learn.adafruit.com/introducing-adafruit-itsybitsy-m4/downloads.

Neither the Itsy M0 nor M4 have a voltage divider for monitoring. So remove the BATTERY pin from the Itsy M0 as well, in your changes.

[tannewt]

Thank you!