arm64: dts: Fix to use standard DT node names for X-Gene 1 and X-Gene 2 platforms

Use devicetree standard node name for I2C (i2c@...),
GFC GPIO (gpio@...), DW GPIO (gpio@...), Standby GPIO (gpio@...).

The DT node name of USB (dwusb@...) still needs to be kept to
maintain backward compatibility with old firmware.

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