r300g: implement hyper-z support. (v4)

r300g: implement hyper-z support. (v4)

This implements fast Z clear, Z compression, and HiZ support for r300->r500
GPUs.

It also allows cbzb clears when fast Z clears are being used for the ZB.

It requires a kernel with hyper-z support.

Thanks to Marek Olšák <maraeo@gmail.com>, who started this off, and Alex Deucher at AMD for providing lots of hints.

v2:
squashed zmask ram size fix]
squashed r300g/blitter: fix Z readback when compressed]

v3:
rebase around texture changes in master - .1 fix more bits

v4:
migrated to using u_mm in r300_texture to manage hiz/zmask rams consistently
disabled HiZ when using OQ
flush z-cache before turning hyper-z off
update hyper-z state on dsa state change
store depthclearvalue across cbzb clears and replace it afterwards.

Signed-off-by: Dave Airlie <airlied@redhat.com>