drm/i915/chv: Enable Render Standby (RC6) for Cherryview

v2: Configure PCBR if BIOS fails allocate pcbr (deepak)

v3: Fix PCBR condition check during CHV RC6 Enable flag set

v4: Fixup PCBR comment msg. (Chris)
    Rebase against latest code (Deak)
    Fixup Spurious hunk (Ben)

v5: Fix PCBR and commentis msg (mika)

v6: Rebase patch on latest nightly (Deepak)

Signed-off-by: Deepak S <deepak.s@linux.intel.com>
Acked-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index e691b30..15653d4 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -1167,6 +1167,8 @@
 #define VLV_IMR		(VLV_DISPLAY_BASE + 0x20a8)
 #define VLV_ISR		(VLV_DISPLAY_BASE + 0x20ac)
 #define VLV_PCBR	(VLV_DISPLAY_BASE + 0x2120)
+#define VLV_PCBR_ADDR_SHIFT	12
+
 #define   DISPLAY_PLANE_FLIP_PENDING(plane) (1<<(11-(plane))) /* A and B only */
 #define EIR		0x020b0
 #define EMR		0x020b4