arm64: dts: apple: add #interrupt-cells property to pinctrl nodes

Required for devices trying to use pinctrl devices as interrupt
controller.

Fixes: 0a8282b8 ("arm64: apple: Add pinctrl nodes")
Signed-off-by: Janne Grunau <j@jannau.net>
Cc: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
Tested-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Hector Martin <marcan@marcan.st>