habanalabs: make sure device mem alloc is page aligned

Working with MMU that supports multiple page sizes requires that mapping
of a page of a certain size will be aligned to the same size (e.g. the
physical address of 32MB page shall be aligned to 32MB).

To achieve this the gen_poll allocation is now using the "align" variant
to comply with the alignment requirements.

Signed-off-by: Ohad Sharabi <osharabi@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>