staging: wlan-ng: add byte order annotation to struct p80211_caphdr

Fixes the following sparse warnings around line 3514 in hfa384x_usb.c:

warning: incorrect type in assignment (different base types)
   expected unsigned int [unsigned] [usertype] version
   got restricted __be32 [usertype] <noident>

Signed-off-by: Aapo Vienamo <aapo.vienamo@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>