OMAPDSS: nec-nl8048 panel: handle gpios in panel driver

OMAPDSS: nec-nl8048 panel: handle gpios in panel driver

The nec-nl8048hl11-01 panel driver leaves gpio configurations to the
platform_enable and disable calls in the platform's board file. These should
happen in the panel driver itself.

Create a platform data struct for the panel, this contains the gpio numbers
used by the panel driver, this struct will be passed to the panel driver as
platform data. The driver will request and configure these gpios rather than
leaving it to platform callbacks in board files.

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

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