dt-bindings: interrupt-controller: renesas,irqc: Add r8a779f0 support

Document support for the Interrupt Controller for External Devices
(INT-EX) in the Renesas R-Car S4-8 (R8A779F0) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/9467a1c67d5d240211f88336973fa968d39cc860.1690446928.git.geert+renesas@glider.be