ARM: dts: armada-38x: label USB and SATA nodes

Recently most nodes got labels to make them referenceable. The USB 3.0
nodes as well as the nodes for the SATA controllers were left out,
rectify the omission.

The labels "sataX" are already used by some boards for the SATA ports,
therefore use "ahciX" to label the SATA controller nodes.

To avoid potential confusion by labeling an USB3.0 controller "usb2" use
usb3_X as labels. This also coincides with the node names themselves
(usb@xxxxx vs usb3@xxxxx).

Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>