radeon: reverse DBG_NO_HYPERZ logic

radeon: reverse DBG_NO_HYPERZ logic

Change the flag to DBG_HYPERZ and reverse the logic
so setting the flag enabled the feature.  This disables
hyperz on r600g and radeonsi by default.  It can be
enabled by setting the env var.  There are just too
many issues with certain apps so leave it disabled for
now until we sort out the issues with the problematic
apps.

Bugs:
https://bugs.freedesktop.org/show_bug.cgi?id=58660
https://bugs.freedesktop.org/show_bug.cgi?id=64471
https://bugs.freedesktop.org/show_bug.cgi?id=66352
https://bugs.freedesktop.org/show_bug.cgi?id=68799
https://bugs.freedesktop.org/show_bug.cgi?id=72685
https://bugs.freedesktop.org/show_bug.cgi?id=73088
https://bugs.freedesktop.org/show_bug.cgi?id=74428
https://bugs.freedesktop.org/show_bug.cgi?id=74803
https://bugs.freedesktop.org/show_bug.cgi?id=74863
https://bugs.freedesktop.org/show_bug.cgi?id=74892
https://bugzilla.kernel.org/show_bug.cgi?id=70411

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: "10.1" "10.0" <mesa-stable@lists.freedesktop.org>
Acked-by: Marek Olšák <marek.olsak@amd.com>