iscsi-target: Drop left-over iscsi_conn->bad_hdr

All REJECT response setup of the rejected payload is now done using
on-demand cmd->buf_ptr allocations.

Go ahead and remove dead iscsi_conn->bad_hdr usage rx_opcode path

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --cc drivers/target/iscsi/iscsi_target.c
Simple merge

diff --cc drivers/target/iscsi/iscsi_target_core.h
Simple merge