v3dv: TFU destination must be UIF

v3dv: TFU destination must be UIF

We had some code that considered the possibility that the destination
might be linear when configuring TFU jobs, but we never actually allow
for this to happen since we avoid hitting these paths in that case, as
the TFU always produces UIF results. Instead, add an assert when
producing the TFU packet to ensure we are expecting a UIF result.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15342>