lima/ppir: improve regalloc spill cost calculation

lima/ppir: improve regalloc spill cost calculation

Now that spilling ops can be inserted into existing instructions, it
makes sense to increase cost to spill registers that would cause the
creation of a new instruction.
Experimental results showed that penalizing too much due to this caused
worse results, however it is beneficial as a tie resolver between
registers with the same number of components.

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