svga: Rework the blit and resource_copy_region functionality v3

svga: Rework the blit and resource_copy_region functionality v3

This work was initially trigged by the fact that imported surfaces may
be backed by other SVGA3D formats than the default. Therefore some fixes were
needed to avoid using the copy_region_vgpu10() functionality for incompatible
SVGA3D formats where the pipe formats were OK. This situation happens when
using dri3.

Also in some situations, for example where a R8G8_UNORM surface is backed by
an SVGA3D_NV12 format, we can't use the copy_region functionality at all and
thus need to fall back to the quad blitter also for the resource_copy_region
function. This situation doesn't happen currently, but will if we start using
video textures.

The patch makes the blit- and copy_region paths similar and the decision whether
to use a certain gpu command should now be easy to locate. Probably the
resource_copy_region path will suffer from a minor additional cpu overhead,
but on the other hand there are more cases now that we accelerate, since
we try harder before falling back to cpu copies / blits.

v2: Addressed review comments and fixed up piglit failures by sometimes
preferring cpu_copy_region() over blit().
v3: Removed a stray test statement. Updated commit message.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>