drm/radeon/dpm: fix display gap programming on SI

Need to set the DISP*_GAP fields as well as the
DISP*_GAP_MCHG fields.  Same as on previous asics.
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/si_dpm.c

@@ -3620,8 +3620,12 @@ static void si_enable_display_gap(struct radeon_device *rdev)
 {
 	u32 tmp = RREG32(CG_DISPLAY_GAP_CNTL);
 
+	tmp &= ~(DISP1_GAP_MASK | DISP2_GAP_MASK);
+	tmp |= (DISP1_GAP(R600_PM_DISPLAY_GAP_IGNORE) |
+		DISP2_GAP(R600_PM_DISPLAY_GAP_IGNORE));
+
 	tmp &= ~(DISP1_GAP_MCHG_MASK | DISP2_GAP_MCHG_MASK);
-	tmp |= (DISP1_GAP_MCHG(R600_PM_DISPLAY_GAP_IGNORE) |
+	tmp |= (DISP1_GAP_MCHG(R600_PM_DISPLAY_GAP_VBLANK) |
 		DISP2_GAP_MCHG(R600_PM_DISPLAY_GAP_IGNORE));
 	WREG32(CG_DISPLAY_GAP_CNTL, tmp);
 }