radeon: enable Hyper-Z on r600g and radeonsi by default

radeon: enable Hyper-Z on r600g and radeonsi by default

This reverts commit 01e637114914453451becc0dc8afe60faff48d84.
Since then many Hyper-Z issues have been fixed or worked around.

Enable Hyper-Z by default so that we get enough feedback for the upcoming
mesa 10.4 release.

If you have issues with Hyper-Z try to disable Hyper-Z using the enviroment
variable R600_DEBUG=nohyperz and please report the issue on the bugtracker.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75011
See also: https://bugs.freedesktop.org/show_bug.cgi?id=75112

Signed-off-by: Andreas Boll <andreas.boll.dev@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>