Staging: wlan-ng: refactor p80211wext.c to reduce text size.

Refactor the wext interface to reduce lines of code & module text size.

- add a helper function p80211wext_getmib
- rename p80211wext_dorequest to p80211wext_setmib
- refactor wext to call the get/set mib helpers and so reduce repeated code.

size reported text reduction :-
   text	   data	    bss	    dec	    hex	filename
   8343	    720	      0	   9063	   2367	p80211wext.o.patch
   9907	    720	      0	  10631	   2987	p80211wext.o.orig

Tested on x86_32 laptop, everything works correctly using NetworkManager,
and iwconfig & iwlist return sensible results when reading from the card.
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>