Use the ib_umem_find_best_pgsz() and rdma_for_each_block() API when
registering an MR instead of coding it in the driver.

ib_umem_find_best_pgsz() is used to find the best suitable page size
which replaces the existing efa_cont_pages() implementation.
rdma_for_each_block() is used to iterate the umem in aligned contiguous
memory blocks.
Reviewed-by: Firas JahJah <firasj@amazon.com>
Reviewed-by: Yossi Leybovich <sleybo@amazon.com>
Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>