Revert "USB: rio500: simplify locking"

This reverts commit d710734b.
This simplification causes a deadlock.

Reported-by:  <syzbot+7bbcbe9c9ff0cd49592a@syzkaller.appspotmail.com>
Fixes: d710734b ("USB: rio500: simplify locking")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20190808092854.23519-1-oneukum@suse.com


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