RDMA/iw_cxgb4: only read markers_enabled mod param once

markers_enabled should be read only once during MPA negotiation.
The present code does read markers_enabled twice during negotiation
which results in setting wrong recv/xmit markers if the markers_enabled is
changed in the middle of negotiation.
With this change the markers_enabled is read only once during MPA
negotiation. recv markers are set based on markers enabled module
parameter and xmit markers are set based on markers flag from the
MPA_START_REQ/MPA_START_REP.

Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>