OMAP3: pandora: revise GPIO configuration

OMAP3: pandora: revise GPIO configuration

Update pandora's GPIO setup code with these changes:
- convert to gpiolib
- set up dual voltage GPIOs to match supply of 1.8V by clearing VMODE1
- add GPIO_IO_PWRDNZ configuration for DM3730 variation of pandora
  (required to enable GPIO 126, 127, and 129 I/O cells in DM3730)
- add wifi reset pulse as recommended by wifi chip's manufacturer
- drop configuration of GPIOs that u-boot doesn't need

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>