ARM: dts: armada-385-linksys: fixup button node names

Buttons don't have a reg property; drop pseudo address and fixup names
of individual button nodes. Also drop #address-cells and #size-cells
properties.

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