anv, crocus, iris: Try unsynchronized userptr if regular one fails

This patch is Jan Beich's downstream workaround for crocus, iris, and anv to work well with Gen < 7. It is required to run Vulkan apps on FreeBSD on Gen < 7.
Link:
https://github.com/freebsd/freebsd-ports/blob/main/graphics/mesa-devel/files/patch-userptr

Authored-by: Jan Beich jbeich@freebsd.org
Reviewed-by: Eleni Maria Stea elene.mst@gmail.com

cc: @jbeich