Fixed ticket:339 (ethernet capability advertisement). We now

Fixed ticket:339 (ethernet capability advertisement).  We now
advertise that we only handle 1000BASE-T, and that we want to send
PAUSE frames, but not receive them.  The flow control resolution is
currently printed out on the serial port when the link comes up.  When
we get what we want, it says "ethernet flow control: WE_TX".  If it
says "ethernet flow control: NONE" unthrottled transmission (e.g.,
usrp2_siggen.py) will be hosed.

git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@10634 221aa14e-8319-0410-a670-987f0aec2ac5