libcopybit: Add missing return statement

Change-Id: Id8011e2dc4f18bc10fe897084ba00d3e5eae77d1
copybit: fix conversion warnings

gcc is chucking out warnings (and with later gcc versions, errors) about conversion from uint32_t to int. we should convert these properly

Change-Id: If93dc0a5355e262559063a96ddb524200a663d54