vulkan/drm_syncobj: Implement WAIT_PENDING with a sync_file lookup

vulkan/drm_syncobj: Implement WAIT_PENDING with a sync_file lookup

The v3dv kernel driver doesn't support timelines yet but we want
threaded submit and that requires WAIT_PENDING.  Fortunately, it should
never sit in this loop for long in practice.  The primary use-case is
sorting out dependencies and these checks will always trivially succeed
for non-shared semaphores because v3dv only has a single queue.

Acked-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15704>