radv: fix DCC enablement since partial MSAA implementation

radv: fix DCC enablement since partial MSAA implementation

dcc_msaa_allowed is always false on GFX9+ and only true on VI
if RADV_PERFTEST=dccmsaa is set. This means DCC was disabled
in some situations where it should not.

This is likely going to fix a performance regression.

Fixes: 2f63b3dd09 ("radv: enable DCC for MSAA 2x textures on VI under an option")
Cc: 18.1 <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>