OMAP: VRFB: convert vrfb to platform device

This patch converts vrfb library into a platform device, in an effort to
remove omap dependencies.

The platform device is registered in arch/arm/plat-omap/fb.c and
assigned resources depending on whether running on omap2 or omap3.

The vrfb driver will parse those resources and use them to access vrfb
configuration registers and the vrfb virtual rotation areas.

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