drm/i915/skl: Mirror what we do on HSW for the power well enable log message

Just to be more consistent with what we do on HSW.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>