r600g: partialy fix texturing from depth buffer + initial support for untiling

r600g: partialy fix texturing from depth buffer + initial support for untiling

Partialy fix texturing from depth buffer, depth buffer is tiled
following different tile organisation that color buffer. This
properly set the tile type & array mode field of texture sampler
when sampling from db resource.

Add initial support to untiling buffer when transfering them,
it's kind of broken by corruption the vertex buffer of previous
draw.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>