r300g: implement ARR opcode

Same as ARL, just has extra rounding.
Useful for st/nine.

Tested-by: Pavel Ondračka <pavel.ondracka@email.cz>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
st/nine: fix DBG typo (trivial)

Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
radeonsi: force NaNs to 0

This fixes incorrect rendering in Unreal Engine demos.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83510

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>