iser-target: Add support for ISCSI_OP_TEXT opcode + payload handling
iser-target: Add support for ISCSI_OP_TEXT opcode + payload handling

This patch adds isert_handle_text_cmd() to handle incoming
ISCSI_OP_TEXT PDU processing, along with isert_put_text_rsp()
for posting ISCSI_OP_TEXT_RSP ib_send_wr response.

It copies ISCSI_OP_TEXT payload using unsolicited payload at
&iser_rx_desc->data[0] into iscsi_cmd->text_in_ptr for usage
with outgoing isert_put_text_rsp() -> iscsit_build_text_rsp()

v2 changes:
  - Let iscsit_build_text_rsp() determine any extra padding

Reported-by: Or Gerlitz <de1b678a59344538ef9f2ddb34a5f9486544e2f9@mellanox.com>
Cc: Or Gerlitz <de1b678a59344538ef9f2ddb34a5f9486544e2f9@mellanox.com>
Cc: Mike Christie <6fe105eefab41990d7ec714c6c25ade3095cdb48@cs.wisc.edu>
Signed-off-by: Nicholas Bellinger <978acd1567d5598152161fdf8bf3ca568f950c9b@linux-iscsi.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs