lima/ppir: lower texture projection

lima/ppir: lower texture projection

Lower texture projection in ppir using nir_lower_tex and nir_lower_tex.
This will insert a mul with the coordinate division before the load
varying.

Even though the lima pp supports projection in the load varying
instruction while loading the coordinates (from a register or a
varying), it requires that both the coordinates and projector be
components in a single register.
nir currently handles them in separate ssa, and attempting to merge them
manually may end up in worse code than just doing the coordinate
division manually. So for now let's just lower the projection to add
support for it in lima.
In the future, an optimization pass may be implemented in lima to ensure
that both coords and projector come in the same register, then this
lowering may be disabled and in this case lima may use the built-in
projection and save the mul instruction from lowering.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Reviewed-by: Qiang Yu <yuq825@gmail.com>