[Intel-gfx] [PATCH] drm/i915: fix ifnullfree.cocci warnings

[Chris Wilson]

Quoting kbuild test robot (2017-06-15 16:23:12)
> drivers/gpu/drm/i915/i915_gem_execbuffer.c:300:2-7: WARNING: NULL check before freeing functions like kfree, debugfs_remove, debugfs_remove_recursive or usb_free_urb is not needed. Maybe consider reorganizing relevant code to avoid passing NULL values.

It exists because it was a stepping towards the compare being not
against NULL.
-Chris