IB/iser: Get rid of un-maintained counters

We don't update those anywhere in the code and they
seem pretty useless (no one seem to care about those).

qp_tx_queue_full: We never should get this
fmr_map_not_avail: We can never get to this
eh_abort_cnt: We don't monitor aborts

Go ahead and remove them.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>