edje: fix backward compatibility issue caused by legacy cursor funcs

edje: fix backward compatibility issue caused by legacy cursor funcs

Summary:
edje_object_part_text_cursor_prev/next/up/down has return value.
It has to return EINA_TRUE when only it successed.
But, when these funcs moved to legacy, it changed to return EINA_TRUE
whenever it fails or success. It must return EINA_FALSE when it fails.
@fix

Test Plan:
- Run test suite
  make check

Reviewers: herdsman, raster, cedric, woohyun

Differential Revision: https://phab.enlightenment.org/D5972

Change-Id: I4290a3a4725bdfdc39f8dcceda559bc484fcf36d