bus: ti-sysc: Add support for disabling module without legacy mode

We must not assert reset for modules with no child device drivers
until in runtime_suspend. Otherwise register access will fail without
legacy mode helping us.

Let's add a flag for disable_on_idle and move the reset driver
handling to runtime suspend and resume. We can then also use the
disable_on_idle flag to reconfigure sysconfig register for PM
modes requesting it.

Let's also make the other flags use bitfield while at it instead of
bool.

Tested-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>