drm/v3d: Use huge tmpfs mountpoint helpers

drm/v3d: Use huge tmpfs mountpoint helpers

Make use of the new drm_gem_huge_mnt_create() and
drm_gem_get_huge_mnt() helpers to avoid code duplication. Now that
it's just a few lines long, the single function in v3d_gemfs.c is
moved into v3d_gem.c.

v3:
- use huge tmpfs mountpoint in drm_device
- move v3d_gemfs.c into v3d_gem.c

v4:
- clean up mountpoint creation error handling

v5:
- fix CONFIG_TRANSPARENT_HUGEPAGE check
- use drm_gem_has_huge_mnt() helper

v8:
- don't access huge_mnt field with CONFIG_TRANSPARENT_HUGEPAGE=n

v9:
- replace drm_gem_has_huge_mnt() by drm_gem_get_huge_mnt()

v10:
- get rid of CONFIG_TRANSPARENT_HUGEPAGE ifdefs

v11:
- remove superfluous comment
- add Maíra and Boris R-bs

Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://patch.msgid.link/20251205182231.194072-7-loic.molinari@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>