RDMA/bnxt_re: Use core helpers to get aligned DMA address

Call the core helpers to retrieve the HW aligned address to use for the
MR, within a supported bnxt_re page size.

Remove checking the umem->hugtetlb flag as it is no longer required. The
new DMA block iterator will return the 2M aligned address if the MR is
backed by 2M huge pages.

Acked-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>