boards: arm: reduce the default drivers for the Arduino Zero

Now that the SAM0 SOC selects the appropriate SAM0 driver for a class,
reduce the drivers that are compiled in by default on the Arduino
Zero.  This reduces the size of `blink` from ~14 KiB to ~10 KiB.

Also add the supported features to arduino_zero.yaml to get more
coverage in the sanity tests.

Signed-off-by: Michael Hope <mlhx@google.com>