net: Change help text to list -netdev instead of -net by default

net: Change help text to list -netdev instead of -net by default

Looking at the output of "qemu-system-xxx -help", you easily get
the impression that "-net" is the preferred way instead of "-netdev"
to specify host network interface, since the "-net" option is
omnipresent but the "-netdev" option is only listed as a one-liner
at the end. This is ugly since "-net" is considered as legacy and
even might be removed one day. Thus, this patch switches the output
to explain the host network interfaces with the "-netdev" option
instead, moving the old "-net" option into some few lines at
the end.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 1431701904-12230-1-git-send-email-thuth@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>