drm/i915: Rename and inline i915_gem_context_get()

i915_gem_context_get() is a very simple wrapper around idr_find(), so
simple that it would be smaller to do the lookup inline. Also we use the
verb 'lookup' to return a pointer from a handle, freeing 'get' to imply
obtaining a reference to the context.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1464098023-3294-3-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index e61b92d..84d9903 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1075,7 +1075,7 @@
 	if (engine->id != RCS && ctx_id != DEFAULT_CONTEXT_HANDLE)
 		return ERR_PTR(-EINVAL);
 
-	ctx = i915_gem_context_get(file->driver_priv, ctx_id);
+	ctx = i915_gem_context_lookup(file->driver_priv, ctx_id);
 	if (IS_ERR(ctx))
 		return ctx;