bus: ti-sysc: avoid toggling power state of module during probe

Current implementation for ti-sysc powers down the module once module
init is complete. However, right after power is disabled, it is enabled
via runtime PM. This is unnecessary so avoid it by re-ordering the
events a bit; move powering down of the module post runtime PM enable
which makes sure the use counts are maintained properly and there is
no extra power down/up sequence for the module.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>