media: atomisp: hmm_bo: Rewrite alloc_private_pages() using pages_array helper funcs

media: atomisp: hmm_bo: Rewrite alloc_private_pages() using pages_array helper funcs

Rewrite alloc_private_pages() using pages_array helper funcs.

Note alloc_pages_bulk_array() skips non NULL pages, so switch
the allocating of the pages pointer array to kcalloc to ensure
the pages are initially all set to NULL.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>