drm/i915: Add missing kerneldoc for 'ent' in i915_driver_init_early

drivers/gpu/drm/i915/i915_drv.c:891: warning: No description found for parameter 'ent'

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180208105449.29880-1-chris@chris-wilson.co.uk


Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>