agx: Put else instructions in the right block

agx: Put else instructions in the right block

According to Dougall's pseudocode, else_icmp operates as:

  if r0l == 0:
    r0l = n
  elif r0l == 1:
    if cc.compare(A[thread], B[thread]):
      r0l = 0
    else:
      r0l = 1

  exec_mask[thread] = (r0l == 0)

Notice that the comparison only happens when r0l == 1, that is, for threads that
are about to enter the else block. Threads that just executed the if body are
still active (r0l = 0) and skip the comparison. As such, the sources of
else_icmp are only read in the else block, and hence the whole instruction
should be placed in the else block for correctness with respect to live range
splitting.

shader-db is a wash, but shows some improvements due to correctly modelling the
liveness of the condition variable.

   total instructions in shared programs: 1778376 -> 1778390 (<.01%)
   instructions in affected programs: 14753 -> 14767 (0.09%)
   helped: 35
   HURT: 39
   Inconclusive result (value mean confidence interval includes 0).

   total bytes in shared programs: 12185018 -> 12185102 (<.01%)
   bytes in affected programs: 101522 -> 101606 (0.08%)
   helped: 35
   HURT: 39
   Inconclusive result (value mean confidence interval includes 0).

   total halfregs in shared programs: 531174 -> 531032 (-0.03%)
   halfregs in affected programs: 2320 -> 2178 (-6.12%)
   helped: 40
   HURT: 1
   Halfregs are helped.

   total threads in shared programs: 18909184 -> 18909440 (<.01%)
   threads in affected programs: 1792 -> 2048 (14.29%)
   helped: 2
   HURT: 0

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