In the future we'll need to support multiple power wells, so prepare for
that here. Create a new power domains struct which contains all
power domain/well specific fields. Since we'll have one lock protecting
all power wells, move power_well->lock to the new struct too.
No functional change.
Signed-off-by: Imre Deak <imre.deak@intel.com> Reviewed-by: Paulo Zanoni <paulo.zanoni@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>