Use bitrev8 for ambassador driver.

Cc: Chas Williams <linux-atm-general@lists.sourceforge.net>
Cc: Giuliano Procida at Madge Networks <gprocida@madge.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>