arm: pia-am335x-apc: fix gpio3_16 signal name

Signed-off-by: Björn Krombholz <b.krombholz@pironex.de>
arm: pia-am335x-apc: switch default baseboard led trigger to mmc0

Signed-off-by: Björn Krombholz <b.krombholz@pironex.de>
arm: pia-am335x: remove newline from bt_en gpio name

Signed-off-by: Björn Krombholz <b.krombholz@pironex.de>
arm: pia-am335x-apc: update defaults for Battery Power GPIO

- battery power should be turned on unless we want to completely turn off
  the system

Signed-off-by: Björn Krombholz <b.krombholz@pironex.de>