radeonsi: Assorted depth/stencil changes ported from r600g.

radeonsi: Assorted depth/stencil changes ported from r600g.

[ Squashed port of the following r600g commits: - Michel Dänzer ]

commit c1e8c845ea9c6f843cc5bba5974668c007799bbc
Author: Marek Olšák <maraeo@gmail.com>
Date:   Sat Jul 7 19:10:00 2012 +0200

    r600g: inline r600_hw_copy_region

commit 4891c5dc64ccd8cf2bf8a8550ae23e1a61806a7d
Author: Marek Olšák <maraeo@gmail.com>
Date:   Mon Jun 25 22:53:21 2012 +0200

    r600g: inline r600_blit_push_depth and use resource_copy_region

    We are going to have a separate resource for depth texturing and transfers
    and this is just a transfer thing.

commit da98bb6fc105e1a2f688a1713ca9e50f0ac8fbed
Author: Marek Olšák <maraeo@gmail.com>
Date:   Mon Jun 25 12:45:32 2012 +0200

    r600g: split flushed depth texture creation and flushing

Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>