doc: boards: atsame54_xpro: Update supported features and pin mapping

The table of supported features for the atsame54_xpro is missing many
peripherals and drivers. The pin mapping list is also incomplete. Update
the table and list to match the set of soc-compatible drivers and the
atsame54_xpro devicetree, respectively.

Signed-off-by: Brandon Del Bel <delbel@umn.edu>