RDMA/umem: Fix ib_umem_find_best_pgsz()

RDMA/umem: Fix ib_umem_find_best_pgsz()

commit 36798d5ae1af62e830c5e045b2e41ce038690c61 upstream.

Except for the last entry, the ending iova alignment sets the maximum
possible page size as the low bits of the iova must be zero when starting
the next chunk.

Fixes: 4a35339958f1 ("RDMA/umem: Add API to find best driver supported page size in an MR")
Link: https://lore.kernel.org/r/20200128135612.174820-1-leon@kernel.org
Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Tested-by: Gal Pressman <galpress@amazon.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>