OMAP buffers are mapped to userspace in write-combining mode by default.
Add support for cached mappings.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

The library is just a wrapper around ioctls. It doesn't provide much
value, and its API is marked as experimental and should thus not be
expected to be stable. As third party library dependencies are always
painful for distributors and packagers, use the ioctls directly for now.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Add OmapCard and OmapFramebuffer classes to utilize omap_bos. Only
non-tiled framebuffer is implemented for now.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>