datapath: omit _mod from module names

datapath: omit _mod from module names

This renames the datapath modules:

  openvswitch_mod -> openvswitch
  brcompat_mod -> brcompat

The first makes the module name consistent with upstream, and the latter
is just for internal consistency.  This makes tools, and documentation
refer to a common module name regardless if it's coming from upstream
linux or built from datapath/ as part of a local build.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Jesse Gross <jesse@nicira.com>