ARM: dts: armada-385: add support for the Linksys WRT1900ACS (Shelby)

The Linksys WRT1900ACS (Shelby) is another Armada 385 based router in
the Linksys WRT AC Series which got released in October 2015.

The file armada-385-linksys-shelby.dts is taken from OpenWrt as-is and
originally authored by Imre Kaloz.

URL: https://github.com/openwrt/openwrt/blob/8466384db1154a107b86bf3ca10b166a21bd81d0/target/linux/mvebu/files/arch/arm/boot/dts/armada-385-linksys-shelby.dts


CC: Imre Kaloz <kaloz@openwrt.org>
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Signed-off-by: Imre Kaloz <kaloz@openwrt.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>