staging: rtlwifi: don't check the return value of debugfs_create_file

We never did anything with the return value, and it does not matter if
the call succeeds or not (it's just debugging code), so don't even check
it.

Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Ping-Ke Shih <pkshih@realtek.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: "Frank A. Cancio Bello" <frank@generalsoftwareinc.com>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>