broadcom/common: retrieve V3D revision number

broadcom/common: retrieve V3D revision number

The subrev field from the hub ident3 register is bumped with every
hardware revision doing backwards incompatible changes so we want to
keep track of this.

Instead of modifying the 'ver' field info to acommodate subrev info,
which would require a lot of changes, simply add a new 'rev' field in
devinfo that we can use when we need to make changes based on the
revision number of a hardware release.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25450>