drm/panfrost: Update io-pgtable API

Convert to io-pgtable's bulk {map,unmap}_pages() APIs, to help the old
single-page interfaces eventually go away. Unmapping heap BOs still
wants to be done a page at a time, but everything else can get the full
benefit of the more efficient interface.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/daef7f8c134d989c55636a5790d8c0fcaca1bae3.1661205687.git.robin.murphy@arm.com