Debug asserts in code-generator-s390.cc are in place to ensure that overflow is only set when dealing with a sub or add opcode. However, the check only looked for kS390_Add/SubWithOverflow32, not kS390_Add/Sub which also sets overflow. This CL adds the second case to this assert check.

R=michael_dawson@ca.ibm.com,jyan@ca.ibm.com,mtbrandyberry@ca.ibm.com,joransiu@ca.ibm.com

BUG=

Review URL: https://codereview.chromium.org/1863983003

Cr-Commit-Position: refs/heads/master@{#35310}