pia_am35x: added new expansion board 'piA_Plus_Messverstaerker'
pia_am35x: -changed pia_mess GPIOs to input
pia35x: disabled pullup/down on gpios for amplifier board

Signed-off-by: Marian Lueder <m.lueder@pironex.de>
Merge remote-tracking branch 'ml/pia35x-ml' into pia35x-3.2-dev

* ml/pia35x-ml:
  pia35x: disabled pullup/down on gpios for amplifier board
  pia_am35x: -changed pia_mess GPIOs to input
  pia_am35x: added new expansion board 'piA_Plus_Messverstaerker'