drm/radeon/dpm: disable ulv support on SI

Causes problems on some boards.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=82889

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/si_dpm.c

@@ -6256,7 +6256,7 @@ static void si_parse_pplib_clock_info(struct radeon_device *rdev,
 	if ((rps->class2 & ATOM_PPLIB_CLASSIFICATION2_ULV) &&
 	    index == 0) {
 		/* XXX disable for A0 tahiti */
-		si_pi->ulv.supported = true;
+		si_pi->ulv.supported = false;
 		si_pi->ulv.pl = *pl;
 		si_pi->ulv.one_pcie_lane_in_ulv = false;
 		si_pi->ulv.volt_change_delay = SISLANDS_ULVVOLTAGECHANGEDELAY_DFLT;