omap: mapphone-panel: First boot logic fixed properly 

We can't skip first_boot logic in mapphone-panel driver completely because in this case dss clocks staying enabled and powerdomains not entering proper states which leads high battery drain for edison and targa platforms.

All we have to do for compatibility is to call dssdev->platform_enable on first boot too if needed.

Tested on edison and targa with JBX kernel without issues. Must be tested on other mapphone-panel devices but it should affects nothing for them.