llvmpipe: Allocate some stuff on demand

The memory footprint of the table has gotten quite out of hand (>3GB in
Control DX12). This patch brings that number down to around 3MB.

Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35959>
1 file changed