Fix bug in simulator which incorrectly interpreted the operands
for CEBR (Float32 compare) as 64-bit doubles.  Add missing
disassembler case for CEBR as well.

R=jyan@ca.ibm.com,michael_dawson@ca.ibm.com,mbrandy@us.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1844473002

Cr-Commit-Position: refs/heads/master@{#35106}