drm/i915: Update intel_ring_begin() to take a request structure

Now that everything above has been converted to use requests, intel_ring_begin()
can be updated to take a request instead of a ring. This also means that it no
longer needs to lazily allocate a request if no-one happens to have done it
earlier.

For: VIZ-5115
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Tomas Elf <tomas.elf@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index c80b59d..a7e58a8 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -509,7 +509,7 @@
 	if (INTEL_INFO(ring->dev)->gen >= 7)
 		len += 2 + (num_rings ? 4*num_rings + 2 : 0);
 
-	ret = intel_ring_begin(ring, len);
+	ret = intel_ring_begin(req, len);
 	if (ret)
 		return ret;