ecore_wl2: do not destroy tizen_position in ecore_wl2_window_hide

ecore_wl2: do not destroy tizen_position in ecore_wl2_window_hide

There was a bug that the window's position was wrong if a window called
ecore_wl2_window_position_set after calling ecore_wl2_window_hide.
In this case, the display server didn't get an information about new position
because the tizen_position was destroyed. When the window was shown again, the
display server sent configure event using old position not new position.
By this, window moved to wrong(old) position.

This patch resolve this problem.

@tizen_only

Change-Id: I28b377ca5fd77106a69f442e4300feb891236d84