lima/ppir: rework emit nir to ppir

lima/ppir: rework emit nir to ppir

The previous code assumed that a ppir node would be created for each nir
instr and used that to add it to the list of nodes and verify success.
This didn't make much sense anymore since some emit paths create
multiple nodes anyway, and this didn't allow for an emit call to not
create any new ppir node while still returning success.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4632>