ether6:  New rotor backend from Jonny, DG9OAA

I have now written a new rotor control based on an Atmel ethernet board
and used with me. It works well so far.

Signed-off-by: Nate Bargmann <n0nb@n0nb.us>
(cherry picked from commit dd5a8f58b69ddd70c575872d82b5569804186dcc)
Patch submission for IC-756

73
Bill.

>From 5209463ba169516543e2666b8b3a98b605c362e6 Mon Sep 17 00:00:00 2001
From: Bill Somerville <g4wjs@classdesign.com>
Date: Sat, 20 Jul 2013 01:45:01 +0100
Subject: [PATCH] All IC-756 varieties have MAIN/SUB VFOs rather than A/B VFOs

In the past IC-756ProIII capabiities have been updated to use MAIN/SUB VFO
commands but as far as I can tell from the user manuals for the IC-756,
IC-756Pro, IC-756Pro2 all varieties have the MAIN/SUB VFOs and need to use
the correct VFO access sub command.

I have an IC-756 and discovered this defect via WSJT-X which as of v1.1
requires split operation setup.

Signed-off-by: Nate Bargmann <n0nb@n0nb.us>
(cherry picked from commit c1212b158d80a3248d6b702a676863b0a5b6c4f1)