drm/i915 more registers for S3 (DSPCLK_GATE_D, CACHE_MODE_0, MI_ARB_STATE)

Failing to preserve the MI_ARB_STATE register was causing FIFO underruns on
the VGA output on my HP 2510p after resume.

Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/char/drm/i915_drv.h b/drivers/char/drm/i915_drv.h
index 360f660..c10d128 100644
--- a/drivers/char/drm/i915_drv.h
+++ b/drivers/char/drm/i915_drv.h
@@ -187,6 +187,9 @@
 	u32 saveIER;
 	u32 saveIIR;
 	u32 saveIMR;
+	u32 saveCACHE_MODE_0;
+	u32 saveDSPCLK_GATE_D;
+	u32 saveMI_ARB_STATE;
 	u32 saveSWF0[16];
 	u32 saveSWF1[16];
 	u32 saveSWF2[3];
@@ -455,6 +458,10 @@
  */
 #define DMA_FADD_S		0x20d4
 
+/* Memory Interface Arbitration State
+ */
+#define MI_ARB_STATE		0x20e4
+
 /* Cache mode 0 reg.
  *  - Manipulating render cache behaviour is central
  *    to the concept of zone rendering, tuning this reg can help avoid
@@ -465,6 +472,7 @@
  * bit of interest either set or cleared.  EG: (BIT<<16) | BIT to set.
  */
 #define Cache_Mode_0		0x2120
+#define CACHE_MODE_0		0x2120
 #define CM0_MASK_SHIFT          16
 #define CM0_IZ_OPT_DISABLE      (1<<6)
 #define CM0_ZR_OPT_DISABLE      (1<<5)
@@ -660,6 +668,8 @@
 /** P1 value is 2 greater than this field */
 # define VGA0_PD_P1_MASK	(0x1f << 0)
 
+#define DSPCLK_GATE_D	0x6200
+
 /* I830 CRTC registers */
 #define HTOTAL_A	0x60000
 #define HBLANK_A	0x60004