arm64: dts: apm: Update GPIO standby controller DT node for X-Gene v2 platforms

xgene-gpio-sb driver now supports configuring some GPIO pins
as interrupt pins. This patch adds the required fields for GPIO
standby controller DT node of X-Gene v2 platform to work with
this new driver change.

Signed-off-by: Quan Nguyen <qnguyen@apm.com>
Signed-off-by: Duc Dang <dhdang@apm.com>