remove redundant material from setup.py

Commit d3fd6b8 introduced an ext_modules
keyword argument to the setup invocation in setup.py, making the

   exttool = Extension(...)

code at the top of setup.py redundant.  Remove the redundant code.

Author: davidmalcolm

setup.py

@@ -6,10 +6,6 @@
 
 version = '0.7'
 
-ethtool = Extension('ethtool',
-		    sources = ['python-ethtool/ethtool.c',
-                               'python-ethtool/etherinfo.c', 'python-ethtool/etherinfo_obj.c'])
-
 def pkgconfig(pkg):
     def _str2list(pkgstr, onlystr):
         res = []