lima/ppir: simplify load uni/temp op lowering and scheduling

lima/ppir: simplify load uni/temp op lowering and scheduling

The load uniform/temporary operations output only to a pipeline
register, which must be consumed by another op in the same instruction
later.
The current implementation delays the decision of who will consume this
result to until the scheduling step. If the consumer node is not able to
use the pipeline register, a mov node may have to be created, during the
scheduler step.

As part of the ppir scheduler simplification, and now that the ppir
scheduler supports pipeline register dependencies, this can be
simplified by always creating a single mov node outputting to a normal
register that can be used directly by all consumers.

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