drm/i915: Clean up L3 SQC register field definitions

No need for hard-coding the register value, the corresponding fields are
defined properly in BSpec.

No functional change.

v2:
- Rebased on BXT L3 SQC tuning patch merged meanwhile.

CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1462280061-1457-3-git-send-email-imre.deak@intel.com
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 227cd2d..6a48f40 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -6737,7 +6737,8 @@
 	 */
 	misccpctl = I915_READ(GEN7_MISCCPCTL);
 	I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
-	I915_WRITE(GEN8_L3SQCREG1, BDW_WA_L3SQCREG1_DEFAULT);
+	I915_WRITE(GEN8_L3SQCREG1, L3_GENERAL_PRIO_CREDITS(30) |
+				   L3_HIGH_PRIO_CREDITS(2));
 	/*
 	 * Wait at least 100 clocks before re-enabling clock gating. See
 	 * the definition of L3SQCREG1 in BSpec.