mlx5: Avoid that mlx5_ib_sg_to_klms() overflows the klms[] array

ib_map_mr_sg() can pass an SG-list to .map_mr_sg() that is larger
than what fits into a single MR. .map_mr_sg() must not attempt to
map more SG-list elements than what fits into a single MR.
Hence make sure that mlx5_ib_sg_to_klms() does not write outside
the MR klms[] array.

Fixes: b005d316

 ("mlx5: Add arbitrary sg list support")
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Max Gurtovoy <maxg@mellanox.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Leon Romanovsky <leonro@mellanox.com>
Cc: Israel Rukshin <israelr@mellanox.com>
Cc: <stable@vger.kernel.org>
Acked-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Doug Ledford <dledford@redhat.com>