cmd/compile: on ARM, make sure *const's AuxInt fit into int32

Previously some of the AuxInt are uint32, which may not fit into
int32. This CL convert them to int32. This does not change the
generated code, but make ssacheck happy.

Pass "toolstash -cmp" for std cmd on ARM.

Fixes #22499.

Change-Id: Ib072d3c14962388bfeb0766c861995d00b4fa7c4
Reviewed-on: https://go-review.googlesource.com/74770
Run-TryBot: Cherry Zhang <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Keith Randall <[email protected]>

Author: cherrymui