iser-target: Fix identification of login rx descriptor type

iser-target: Fix identification of login rx descriptor type

Orabug: 23331107

[ Upstream commit b89a7c25462b164db280abc3b05d4d9d888d40e9 ]

Once connection request is accepted, one rx descriptor
is posted to receive login request. This descriptor has rx type,
but is outside the main pool of rx descriptors, and thus
was mistreated as tx type.

Signed-off-by: Jenny Derzhavetz <jennyf@mellanox.com>
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Cc: stable@vger.kernel.org # v3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 3c6961458165c0ec909d68191bff4de7bdf50549)

Signed-off-by: Dan Duval <dan.duval@oracle.com>