Even though ARC cores itself don't have any power management except SLEEP
state it's possible to use power management features of selected peripherals.

For example USB OTG requires PM_RUNTIME which is only available if
kernel/power/Kconfig is sourced by architecture.
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>