cpu-o3: Resolve circular buffer issue for LSQ

--since int is only 4 bytes, while ssize_t is 8 bytes in 64bit
  system. so 0x80000000 is regarded as negative value.

Jira Issue:: https://gem5.atlassian.net/browse/GEM5-1203

Change-Id: I74b3785b29751f777f5e154692fa60bf62b37b9f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/58649
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
4 files changed