drm/gem-shmem: Refactor drm_gem_shmem_try_map_pmd()

drm/gem-shmem: Refactor drm_gem_shmem_try_map_pmd()

The current mmap page-fault handler requires some changes before it
can track folio access.

Call to folio_test_pmd_mappable() into the mmap page-fault handler
before calling drm_gem_shmem_try_map_pmd(). The folio will become
useful for tracking the access status.

Also rename drm_gem_shmem_try_map_pmd() to _try_insert_pfn_pmd()
and only pass the page fault and page-frame number. The new name and
parameters make it similar to vmf_insert_pfn_pmd().

No functional changes. If PMD mapping fails or is not supported,
insert a regular PFN as before.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patch.msgid.link/20260227114509.165572-5-tzimmermann@suse.de