Add few cases to test the dynamic allocation flow of __sg_alloc_table_from_pages. Link: https://lore.kernel.org/r/20201115120650.139277-1-leon@kernel.org Signed-off-by: Maor Gottlieb <maorg@nvidia.com> Signed-off-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>