soc: ti: omap-prm: Add pm_clk for genpd

In order to probe l3 and l4 interconnects with simple-pm-bus, we want
genpd to manage the clocks for the interconnects. For interconnect target
modules, we already have ti-sysc manage the clocks so let's skipe managing
clocks for ti-sysc modules.

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