aco/optimizer: don't propagate subdword temps of different size

It could happen that due to inconsistent copy-propagation

  v1 = p_parallelcopy v2b

instructions were left after optimization on GFX8.

Cc: 20.3
Cc: 21.0

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8260>
(cherry picked from commit 856fd4750daf23ac3f8f40278cf685f36661c19f)
2 files changed