meta-quanta: s6q: Add usb0 network interface

1. Fix the sytle of systemd-conf.bbappend to wrap with 80 characters.
2. Add usb0 network interface.
3. Disable ipv4 link-local address to avoid routing problems.

Tested:
Set the host's network interface to a link-local address and
successfully communicate with the BMC via usb0.

Signed-off-by: Jerry Wan <jerry.wan@quantatw.com>
Change-Id: I9e6a9946a2beb8cf85872abe1919e92052fe46cc
diff --git a/meta-quanta/meta-s6q/recipes-phosphor/images/obmc-phosphor-image.bbappend b/meta-quanta/meta-s6q/recipes-phosphor/images/obmc-phosphor-image.bbappend
new file mode 100644
index 0000000..3c1f006
--- /dev/null
+++ b/meta-quanta/meta-s6q/recipes-phosphor/images/obmc-phosphor-image.bbappend
@@ -0,0 +1 @@
+OBMC_IMAGE_EXTRA_INSTALL:append:s6q = " usb-ethernet-gadget"