bus: ti-sysc: Change return types of functions

Change return type of functions sysc_check_one_child() and
sysc_check_children() from int to void as neither ever returns an error.
Modify call sites of both functions accordingly.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>