mac80211: clear subdir_stations when removing debugfs
If we don't do this, and we then fail to recreate the debugfs
directory during a mode change, then we will fail later trying
to add stations to this now bogus directory:
BUG: unable to handle kernel NULL pointer dereference at
0000006c
IP: [<
c0a92202>] mutex_lock+0x12/0x30
Call Trace:
[<
c0678ab4>] start_creating+0x44/0xc0
[<
c0679203>] debugfs_create_dir+0x13/0xf0
[<
f8a938ae>] ieee80211_sta_debugfs_add+0x6e/0x490 [mac80211]
Cc: stable@kernel.org
Signed-off-by: Tom Hughes <tom@compton.nu>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>