RDMA/umem: Remove hugetlb flag

The drivers i40iw and bnxt_re no longer dependent on the hugetlb flag. So
remove this flag from ib_umem structure.

Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>