This will be needed by the next patch too so factor it out.

No functional change.
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466084243-5388-4-git-send-email-imre.deak@intel.com