IB/SRP: Avoid using IB_MR_TYPE_SG_GAPS

Tests have shown that the following error message is reported when
using SG-GAPS registration with an mlx5 adapter:

scsi host1: ib_srp: failed RECV status WR flushed (5) for CQE ffff880bd4270eb0
00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000
00000000 0f007806 2500002a ad9fafd1
scsi host1: ib_srp: reconnect succeeded
mlx5_0:dump_cqe:262:(pid 7369): dump error cqe
00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000
00000000 00000000 00000000 00000000
00000000 0f007806 25000032 00105dd0
scsi host1: ib_srp: failed FAST REG status memory management operation error (6) for CQE ffff880b92860138

Hence avoid using SG-GAPS memory registrations. Additionally,
always configure the blk_queue_virt_boundary() to avoid to trigger
a mapping failure when using adapters that support SG-GAPS (e.g.
mlx5).

Fixes: commit ad8e66b4 ("IB/srp: fix mr allocation when the device supports sg gaps")
Fixes: commit 509c5f33 ("IB/srp: Prevent mapping failures")
Reported-by: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Israel Rukshin <israelr@mellanox.com>
Cc: Max Gurtovoy <maxg@mellanox.com>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Mark Bloch <markb@mellanox.com>
Cc: Yuval Shaia <yuval.shaia@oracle.com>
Cc: <stable@vger.kernel.org> # 4.7+
Signed-off-by: Doug Ledford <dledford@redhat.com>