[PATCH] zd1211rw: Removes wrong assertions

Checking whether a mutex is not locked directly before
mutex_lock() is called, doesn't make sense. The whole point of
mutex_lock() is to block, if the mutex is locked.

Signed-off-by: Ulrich Kunitz <kune@deine-taler.de>
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>