ieee802154: hwsim: using right kind of iteration

This patch fixes the error path to unsubscribe all other phy's from
current phy. The actually code using a wrong kind of list iteration may
copied from the case to unsubscribe the current phy from all other
phy's.

Cc: Stefan Schmidt <stefan@datenfreihafen.org>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: f25da51f ("ieee802154: hwsim: add replacement for fakelb")
Signed-off-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>