Link the ARM GIC to the INTC-SYS module clock, and add it to the SYSC
"always-on" PM Domain, so it can be power managed using that clock.

Note that currently the GIC-400 driver doesn't support module clocks nor
Runtime PM, so this must be handled as a critical clock.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>