p54: Move LMAC interface definitions

Copy the LMAC Interface specific definitions from p54common.h into a new file lmac.h
Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>