OMAP2/3/4: DSS2: Enable Display SubSystem as modules

Enabling all the display interface options to be built as module
And enabling all the display panels to be built as modules.

Signed-off-by: Samreen <samreen@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>