agx: Don't lower load_local_invocation_index

agx: Don't lower load_local_invocation_index

We have an SR for it, which can save a bit of math. This came up while working
on the spiller.

   total instructions in shared programs: 1778396 -> 1778376 (<.01%)
   instructions in affected programs: 3036 -> 3016 (-0.66%)
   helped: 10
   HURT: 3
   Instructions are helped.

   total bytes in shared programs: 12185182 -> 12185018 (<.01%)
   bytes in affected programs: 38640 -> 38476 (-0.42%)
   helped: 18
   HURT: 2
   Bytes are helped.

   total halfregs in shared programs: 531218 -> 531174 (<.01%)
   halfregs in affected programs: 471 -> 427 (-9.34%)
   helped: 6
   HURT: 0
   Halfregs are helped.

   total threads in shared programs: 18909056 -> 18909184 (<.01%)
   threads in affected programs: 1280 -> 1408 (10.00%)
   helped: 2
   HURT: 0

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24635>