libertas: tune debug code

[Holger Schurig]

* 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 at mail.mn-solutions.de>

http://git.infradead.org/?p=users/schurig/libertas-cleanups-2.6.git;a=commitdiff;h=ab4c0f580170e412e5038cace8bc64ce2b7e7a33;hp=1135f2e93bd1d1b5d4e7a7a1e8b2be49cebaa25f