edje_entry: prevent incorrect cursor position during preedit

edje_entry: prevent incorrect cursor position during preedit

due to the influence of elm_entry_filter_limit_size,
"cursor_pos" from imf and "end_pos - start_pos" may be different.
in particular, if the preedit string can not be entered at all due to filter,
cursor_pos is larger than 0, so the cursor moves to an unintended position.

This patch avoids the issue by moving the cursor's position to end_pos in this case.

@tizen_fix

Change-Id: Ie7ad48ad02ecbf26a0bedab960cd0bf9042a5995
Signed-off-by: Bowon Ryu <bowon.ryu@samsung.com>