soc: ti: omap-prm: Allow hardware supported retention when idle

When moving the l4 interconnect instances to probe with simple-pm-bus and
genpd, we will have l4per and core domains stop idling unless we configure
the domain bits to allow retention when idle.

As the TI SoCs have hardware autoidle capabilities, this is safe to do.
The domains will only enter retention on WFI when none of the devices on
the domain block autoidle in the hardware. This follows what we are
already currently doing.

Cc: Santosh Shilimkar <ssantosh@kernel.org>
Cc: Tero Kristo <kristo@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>