MFC r215432:

MFC r215432:
  MCP55 is the only NVIDIA controller that supports VLAN tag
  insertion/stripping and it also supports TSO over VLAN. Implement
  TSO over VLAN support for MCP55 controller.

  While I'm here clean up SIOCSIFCAP ioctl handler. Since nfe(4)
  sets ifp capabilities based on various hardware flags in device
  attach, there is no need to check hardware flags again in
  SIOCSIFCAP ioctl handler. Also fix a bug which toggled both TX and
  RX checksum offloading even if user requested either TX or RX
  checksum configuration change.

  Tested by:	Rob Farmer ( rfarmer <> predatorlabs dot net )

git-svn-id: svn://svn.freebsd.org/base/stable/8@218874 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f