p54: integrate parts of lmac_longbow.h and other parts of stlc45xx

This patch removes most/all? of the "magic" numbers and unknown structure
variables inside the code and replaces them with meaningful prototypes.

(Plus a one line warning fix from Larry Finger <Larry.Finger@lwfinger.net>.)

Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>