Fixed 2 occurrences of setCompareMode being used instead
of setImmutableFormat and added a missing break statement.

Change-Id: I1013d0983220ba155dcd4f6255c6e089f03e7fc8
Reviewed-on: https://swiftshader-review.googlesource.com/4016Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>