OMAPDSS: sharp-ls panel: remove platform_enable/disable callbacks

The sharp-ls panel driver now manages the gpios required to configure the panel.
This was previously done in omap_dss_device's platform_enable/disable callbacks
defined in board files using this panel.

All the board files using this panel now pass the gpio information as platform
data via the panel_sharp_ls037v7dw01_data struct, which is needed by the panel
driver to configure the gpios connected to the panel. Hence, the
platform_enable/disable ops can be safely removed now.

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