[PATCH] libertas: tune debug code

* renamed module parameter back to libertas_debug
* change from bit shifts to constants, that way it's easier to look at the
    source and specify the libertas_debug=0xXXXX module parameter
* moved module_param from fw.c to main.c, where it belongs better

Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>