drm/i915: Rename i915_gem_context_reference/unreference()

As these are wrappers around kref_get/kref_put() it is preferable to
follow the naming convention and use the same verb get/put in our
wrapper names for manipulating a reference to the context.

s/i915_gem_context_reference/i915_gem_context_get/
s/i915_gem_context_unreference/i915_gem_context_put/

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: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1469005202-9659-3-git-send-email-chris@chris-wilson.co.uk
Link: http://patchwork.freedesktop.org/patch/msgid/1469017917-15134-2-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 f6724ae..551dd4f 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1509,7 +1509,7 @@
 		goto pre_mutex_err;
 	}
 
-	i915_gem_context_reference(ctx);
+	i915_gem_context_get(ctx);
 
 	if (ctx->ppgtt)
 		vm = &ctx->ppgtt->base;
@@ -1520,7 +1520,7 @@
 
 	eb = eb_create(args);
 	if (eb == NULL) {
-		i915_gem_context_unreference(ctx);
+		i915_gem_context_put(ctx);
 		mutex_unlock(&dev->struct_mutex);
 		ret = -ENOMEM;
 		goto pre_mutex_err;
@@ -1664,7 +1664,7 @@
 
 err:
 	/* the request owns the ref now */
-	i915_gem_context_unreference(ctx);
+	i915_gem_context_put(ctx);
 	eb_destroy(eb);
 
 	mutex_unlock(&dev->struct_mutex);