arm: omap: board-overo: use lb035q02 dpi panel's gpio handling

The overo board file currently requests gpios required by the lb035q02 panel,
and provides platform_enable/disable callbacks to configure them.

These tasks have been moved to the lb035q02 dpi panel driver itself and should
be removed from the board files.

The lb035q02 panel driver uses generic dpi panel's platform data struct
internally. Remove the gpio requests and the platform callbacks from the board
file. Add the gpio information to the generic dpi panel platform data struct so
that it's passed to the panel driver.

Signed-off-by: Archit Taneja <archit@ti.com>
Cc: Tony Lindgren <tony@atomide.com>