USB: mon: kill BKL usage

compat_ioctl does not use the BKL, so I assume that
the native function does not need it either.

The open function is already protected by the
driver's mutex, the BKL is probably not needed
here either.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>