Pass the type we want to simplify. No functional changes.

v2: s/dev_priv/i915/g (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181017093539.5468-1-jani.nikula@intel.com