drm/i915/icl: Do not change reserved registers related to PSR2

For ICL the bit 12 of CHICKEN_TRANS is reserved so we should not
touch it and as by default VSC_DATA_SEL_SOFTWARE_CONTROL is already
unset in gen10 + GLK we can just drop it and fix for both gens.

Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181204003403.23361-5-jose.souza@intel.com

drivers/gpu/drm/i915/intel_psr.c

@@ -649,17 +649,14 @@ static void intel_psr_enable_source(struct intel_dp *intel_dp,
 	if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv))
 		hsw_psr_setup_aux(intel_dp);
 
-	if (dev_priv->psr.psr2_enabled) {
+	if (dev_priv->psr.psr2_enabled && (IS_GEN9(dev_priv) &&
+					   !IS_GEMINILAKE(dev_priv))) {
 		i915_reg_t reg = gen9_chicken_trans_reg(dev_priv,
 							cpu_transcoder);
 		u32 chicken = I915_READ(reg);
 
-		if (IS_GEN9(dev_priv) && !IS_GEMINILAKE(dev_priv))
-			chicken |= (PSR2_VSC_ENABLE_PROG_HEADER
-				   | PSR2_ADD_VERTICAL_LINE_COUNT);
-
-		else
-			chicken &= ~VSC_DATA_SEL_SOFTWARE_CONTROL;
+		chicken |= PSR2_VSC_ENABLE_PROG_HEADER |
+			   PSR2_ADD_VERTICAL_LINE_COUNT;
 		I915_WRITE(reg, chicken);
 	}