ARM: dts: armada-38x: Add gpio-ranges for pin muxing

GPIOs are configured by pinmux driver, so add corresponding references.

Fixes: 0d3d96ab ("ARM: mvebu: add Device Tree description of the Armada 380/385 SoCs")
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>