drm/i915/gen7: Clear all EU/L3 residual contexts

On gen7 and gen7.5 devices, there could be leftover data residuals in
EU/L3 from the retiring context. This patch introduces workaround to clear
that residual contexts, by submitting a batch buffer with dedicated HW
context to the GPU with ring allocation for each context switching.

This security mitigation changes does not triggers any performance
regression. Performance is on par with current drm-tips.

v2: Add igt generated header file for CB kernel assembled with Mesa tool
and addressed use of Kernel macro for ptr_align comment.

v3: Resolve Sparse warnings with newly generated, and imported CB
kernel.

v4: Include new igt generated CB kernel for gen7 and gen7.5. Also
add code formatting and compiler warnings changes (Chris Wilson)

Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Prathap Kumar Valsan <prathap.kumar.valsan@intel.com>
Signed-off-by: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
Cc: Chris Wilson <chris.p.wilson@intel.com>
Cc: Balestrieri Francesco <francesco.balestrieri@intel.com>
Cc: Bloomfield Jon <jon.bloomfield@intel.com>
Cc: Dutt Sudeep <sudeep.dutt@intel.com>
Acked-by: Chris Wilson <chris@chris-wilso.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200306000957.2836150-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/Makefile

@@ -80,6 +80,7 @@ gt-y += \
 	gt/debugfs_gt.o \
 	gt/debugfs_gt_pm.o \
 	gt/gen6_ppgtt.o \
+	gt/gen7_renderclear.o \
 	gt/gen8_ppgtt.o \
 	gt/intel_breadcrumbs.o \
 	gt/intel_context.o \