DRM/Radeon: Fix primary DAC Load Detection for RV100 chips.

For Radeon 7500 ATI recommends a DAC_FORCE value of 0x1ac. This value
works better on ES1000 (RV100) chips, too, as it doesn't produce any false
positives on any cards I have tested. Therefore let's assume that this
value is good for all RV100 and RV200 chipset generations.
Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_legacy_encoders.c

@@ -662,6 +662,8 @@ static enum drm_connector_status radeon_legacy_primary_dac_detect(struct drm_enc
 
 	if (ASIC_IS_R300(rdev))
 		tmp |= (0x1b6 << RADEON_DAC_FORCE_DATA_SHIFT);
+	else if (ASIC_IS_RV100(rdev))
+		tmp |= (0x1ac << RADEON_DAC_FORCE_DATA_SHIFT);
 	else
 		tmp |= (0x180 << RADEON_DAC_FORCE_DATA_SHIFT);