ARM: mvebu: Correct unit address for linksys

The USB2 port for Armada 38x is defined to be at 58000, not at
50000.

Cc: <stable@vger.kernel.org>
Fixes: 2d0a7add ("ARM: Kirkwood: Add support for many Synology NAS devices")
Signed-off-by: Patrick Uiterwijk <patrick@puiterwijk.org>
Acked-by: Imre Kaloz <kaloz@openwrt.org>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>