ARM: dts: Enable interrupt support for cygnus crmu gpio driver

The M0 processor handles interrupts for the always-on CRMU GPIO
controller. Setting the CRMU GPIO driver with the mailbox controller as
the interrupt parent allows the mailbox controller to forward interrupts
from the M0 to the GPIO driver for processing.
Reviewed-by: Jonathan Richardson <jonathan.richardson@broadcom.com>
Tested-by: Jonathan Richardson <jonathan.richardson@broadcom.com>
Reviewed-by: Vikram Prakash <vikram.prakash@broadcom.com>
Reviewed-by: Shreesha Rajashekar <shreesha.rajashekar@broadcom.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
Signed-off-by: Jonathan Richardson <jonathan.richardson@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm/boot/dts/bcm-cygnus.dtsi

@@ -130,6 +130,9 @@ gpio_crmu: gpio@03024800 {
 			ngpios = <6>;
 			#gpio-cells = <2>;
 			gpio-controller;
+			interrupt-controller;
+			interrupt-parent = <&mailbox>;
+			interrupts = <0>;
 		};
 
 		i2c0: i2c@18008000 {