mfd: Add sharing for cs5535 acpi/pms cells

This enables sharing of cs5535-mfd cells via the new mfd_shared_* API.
Hooks for enable/disble of resources are added, with refcounting of
resources being automatically handled so that cs5535_mfd_res_enable/disable
are only called when necessary.

Clients of cs5535-mfd (in this case, olpc-xo1.c) are also modified to
use the mfd_shared API.  The platform drivers are also renamed to
olpc-xo1-{pms,acpi}, and resource enabling/disabling is replaced
with mfd_shared API calls.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>