ARM: dts: kirkwood: Fixup pcie DT warnings

PCIe has a range property, so the unit name should contain an address.
Make use of the label to enable individual PCIe busses. Also, fixup
the synology dtsi file which added a label pcie2 rather than using the
existing pcie1 label.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>