mesa_glinterop: make GL interop version field bidirectional

mesa_glinterop: make GL interop version field bidirectional

This allows clear and easy communication between the two.

Caller: Requesting information (struct vN)
Callee: I know how to deal with older version (vN-1) only. Here is your
data and the version I support.
Caller: Older version ? Sure I'll cap all access to the fields provided
by the older version (vN-1)

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-by: Tom Stellard <thomas.stellard@amd.com>