arm64: dts: imx8mq: Add missing interrupts to GPC

The i.MX General Power Controller v2 device node was missing interrupts
property necessary to route its interrupt to GIC.  This also fixes the
dbts_check warnings like:

  arch/arm64/boot/dts/freescale/imx8mq-evk.dt.yaml: gpc@303a0000:
    {'compatible': ... '$nodename': ['gpc@303a0000']} is not valid under any of the given schemas
  arch/arm64/boot/dts/freescale/imx8mq-evk.dt.yaml: gpc@303a0000: 'interrupts' is a required property

Fixes: fdbcc04d ("arm64: dts: imx8mq: add GPC power domains")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>