Move the old iSCSI initiator source to a more appropriate place
(sys/dev/iscsi_initiator/ instead of sys/dev/iscsi/initiator/), to make
room for the new one.  This is also more logical location (kernel module
being named iscsi_initiator.ko, for example).  There is no ongoing work
on this I know of, so it shouldn't make life harder for anyone.

There are no functional changes, apart from "svn mv" and adjusting paths.