drm/i915: Unify request submission

Move request submission from emit_request into its own common vfunc
from i915_add_request().

v2: Convert I915_DISPATCH_flags to BIT(x) whilst passing
v3: Rename a few functions to match.
v4: Reenable execlists submission after disabling guc.
v5: Be aware that everyone calls i915_guc_submission_disable()!

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1469432687-22756-23-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470174640-18242-14-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 33e0193..bdd764a 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -95,6 +95,8 @@
 /* Execlists */
 int intel_sanitize_enable_execlists(struct drm_i915_private *dev_priv,
 				    int enable_execlists);
+void intel_execlists_enable_submission(struct drm_i915_private *dev_priv);
+
 struct i915_execbuffer_params;
 int intel_execlists_submission(struct i915_execbuffer_params *params,
 			       struct drm_i915_gem_execbuffer2 *args,