ENGR00177359 - EPDC fb: Add EPDC support to SabreSD board

ENGR00177359 - EPDC fb: Add EPDC support to SabreSD board

- Change EPDC pad groups to have one for EPDC enable and one
for EPDC disable.
- Add EPDC and Maxim 17135 structures and functions to SabreSD
board file.  Code pulled in with minimal change from ARM2 board
file.
  One exception: Had to remove regulator_has_full_constraints()
  from max17135_regulator_init() to prevent PFUZE from disabling
  regulators and removing power from the board at the end of
  kernel initialization.

Signed-off-by: Danny Nold <dannynold@freescale.com>