v3dv/meson: add v71 hw generation

v3dv/meson: add v71 hw generation

Starting point for v71 version inclusion.

This just adds it as one of the versions to be compiled (on meson),
updates the v3dX/v3dv_X macros, and update the code enough to get it
compiling when building using the two versions. For any packet not
available on v71 we just provide a generic asserted placeholder of
generation not supported.

Any real v71 support will be implemented on following commits.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25450>