dri: Rework planar image interface

dri: Rework planar image interface

As discussed with Kristian on #wayland. Pushes the decision of components into
the dri driver giving it greater freedom to allow t to implement YUV samplers
in hardware, and which mode to use.

This interface will also allow drivers like SVGA to implement YUV surfaces
without the need to sub-allocate and instead send 3 seperate buffers for each
channel, currently not implemented.

I have tested these changes on Gallium Svga. Scott tested them on both intel
and Gallium Radeon. Kristan and Pekka tested them on intel.

v2: Fix typo in dri2_from_planar.
v3: Merge in intel changes.

Tested-by: Scott Moreau <oreaus@gmail.com>
Tested-by: Pekka Paalanen <ppaalanen@gmail.com>
Tested-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Signed-off-by: Jakob Bornecrantz <jakob@vmware.com>