Fix getting wrong tensor list for COND_IF during deserialization

Also change COND_IF IR format back to generic form in lit test.
Since ERROR_IF checks are added in MLIR COND_IF op verifier. The
existing simplified form is not supported anymore.

Change-Id: If0a303303ac48af63f016eed833fdcf9dd4aaeb9
Signed-off-by: TatWai Chong <tatwai.chong@arm.com>