broadcom/qpu: add pack/unpack support for v71

broadcom/qpu: add pack/unpack support for v71

Note that we provide new v71 alu pack/unpack methods. As there are a
lot that it is equivalent, initially we tried to use existing methods
as template and add version checks on the existing methods. At some
early point that become just really unreadable, so it become better to
just provide new methods, even if v42 and v71 methods have a really
similar structure.

Note that we have splitted the op tables, and created a two (add/mul)
for v71. As the description struct include versioning info, we could
have just used one table. But, specially with the add table, there are
a lot of differences with v71. So it is slightly tidier this
way. Also, taking into account that we do a linear search on the
tables, this can be even justified by performance.

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