staging: wlan-ng: rename DIDmib_cat_p2 in p80211metadef.h

Rename DIDmib_cat_p2 in p80211metadef.h to DIDMIB_CAT_P2 to fix "Avoid
CamelCase" message from checkpatch and conform to the coding style
guidelines.

Signed-off-by: Tim Collier <osdevtc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>