habanalabs: fix mask to obtain page offset

When converting virtual address to physical we need to add correct
offset to the physical page.

For this we need to use mask that include ALL bits of page offset.

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