rc80211_pid fails to remove debugfs files

[Michael Buesch <mb@bu3sch.de>]

The rc80211_pid fails to remove the debugfs files properly.
In debugfs I see phyX directories for PHYs that are long gone.
The only content is the rc80211_pid directory with its files.

Last time I looked through the PID code I saw that it does not
do proper error checking for the creation of debugfs files.
But error checking is important, as it _will_ otherwise result
in unpredicted behaviour. Debugfs is pretty nasty. :)
For example if creation of the root directory failed, it will
put the files all into the debugfs root. And yes, this _does_
happen. We had similiar problems and bugreports from people
in b43.

So please add errorchecking.

-- 
Greetings Michael.