arm64: dts: imx8mp: Fix missing GPC Interrupt

[ Upstream commit b3b75ac ]

The GPC node references an interrupt parent, but it doesn't
state the interrupt itself.  According to the TRM, this IRQ
is 87. This also eliminate an error detected from dt_binding_check

Fixes: fc0f051 ("arm64: dts: imx8mp: add GPC node with GPU power domains")
Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/arm64/boot/dts/freescale/imx8mp.dtsi

@@ -523,6 +523,7 @@
 				compatible = "fsl,imx8mp-gpc";
 				reg = <0x303a0000 0x1000>;
 				interrupt-parent = <&gic>;
+				interrupts = <GIC_SPI 87 IRQ_TYPE_LEVEL_HIGH>;
 				interrupt-controller;
 				#interrupt-cells = <3>;