DRM/Radeon: Fix Load Detection on legacy primary DAC.

An uninitialized variable led to broken load detection.
Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/radeon_legacy_encoders.c

@@ -671,6 +671,7 @@ static enum drm_connector_status radeon_legacy_primary_dac_detect(struct drm_enc
 	tmp |= RADEON_DAC_RANGE_CNTL_PS2 | RADEON_DAC_CMP_EN;
 	WREG32(RADEON_DAC_CNTL, tmp);
 
+	tmp = dac_macro_cntl;
 	tmp &= ~(RADEON_DAC_PDWN_R |
 		 RADEON_DAC_PDWN_G |
 		 RADEON_DAC_PDWN_B);