[enco] Use valid bag size during DataLayoutConversion (#1933)

[enco] Use valid bag size during DataLayoutConversion (#1933)

* [enco] Use valid bag size during DataLayoutConversion

The current implementation of "clone_feature" in data layout conversion
pass creates a new bag whose size is same as the size of a corresponding
bag.

However, this implementation may result in invalid bag mapping, especially
when the corresponding bag uses broadcasting layout (i.e. there are multiple
feature indices that map to one element in a bag).

This commit revises this buggy implementation of "clone_feature".

Signed-off-by: Jonghyun Park <jh1302.park@samsung.com>
* Do NOT declare unused oldbag variable