OMAPDSS: picodlp panel: handle gpio data in panel driver

The picodlp panel driver leaves gpio requests to the platform's board file.
These should happen in the panel driver itself.

A platform data struct called picodlp_panel_data already exists to hold gpio
numbers and other platform data. Request all the gpios in the panel driver so
that the board files which use the the panel don't need to do it.

This will help in removing the need for the panel drivers to have platform
related callbacks.

Signed-off-by: Archit Taneja <archit@ti.com>