drm/i915: Move MMCD_MISC_CTRL from context w/a to standard

Looking at gem_workarounds shows us that MMCD_MISC_CTRL is not restored
following a suspend-resume cycle. This implies that MMCD_MISC_CTRL is
not stored in the context, but is an ordinary register w/a that we need to
restore during init_hw.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171004124153.14142-1-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -980,7 +980,11 @@ static int gen9_init_workarounds(struct intel_engine_cs *engine)
 				  GEN9_PBE_COMPRESSED_HASH_SELECTION);
 		WA_SET_BIT_MASKED(GEN9_HALF_SLICE_CHICKEN7,
 				  GEN9_SAMPLER_HASH_COMPRESSED_READ_ADDR);
-		WA_SET_BIT(MMCD_MISC_CTRL, MMCD_PCLA | MMCD_HOTSPOT_EN);
+
+		I915_WRITE(MMCD_MISC_CTRL,
+			   I915_READ(MMCD_MISC_CTRL) |
+			   MMCD_PCLA |
+			   MMCD_HOTSPOT_EN);
 	}
 
 	/* WaClearFlowControlGpgpuContextSave:skl,bxt,kbl,glk,cfl */