MFC r207375-207377.

MFC r207375-207377.
r207375:
  Preserve unknown bits of RX MAC control register when driver
  programs RX filter configuration. It seems RX MAC control register
  is one of key registers to get various offloading features as well
  as performance. Blindly clearing unrelated bits can result in
  unexpected results.

  Tested by:    xclin <xclin <> cs dot nctu dot edu dot tw >

r207376:
  Remove wrong link state chage.

r207377:
  Explicitly marks SiS190 to differentiate it from SiS191.

git-svn-id: svn://svn.freebsd.org/base/stable/8@207710 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f