dt-bindings: ti_sci_pm_domains: Add support for exclusive and shared access

TISCI protocol supports for enabling the device either with exclusive
permissions for the requesting host or with sharing across the hosts.
There are certain devices which are exclusive to Linux context and
there are certain devices that are shared across different host contexts.
So add support for getting this information from DT by increasing
the power-domain cells to 2.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>