staging: wlan-ng: Remove unused struct p80211macarray definition

struct p80211macarray is defined but is never used. Remove the unused
struct declaration.
Issue identified as part of coccicheck based code analysis.

Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Suggested-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Deepak R Varma <drv@mailo.com>
Link: https://lore.kernel.org/r/b42eff9b8f73542bc9015948e5e4684416982e1b.1667308828.git.drv@mailo.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>