[SCSI] iscsi: rename some proto defs

[SCSI] iscsi: rename some proto defs

From: hare@suse.de

for a proper alignment between open-iscsi and iscsitarget the
definitions in include/iscsi_proto.h do not match exactly.

With this patch it's possible to have iscsitarget use
'include/iscsi_proto.h' instead of its own iscsi_hdr.h.

Signed-off-by: Alex Aizman <itn780@yahoo.com>
Signed-off-by: Dmitry Yusupov <dmitry_yus@yahoo.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>