refactor code to handle sync_client_geometry_add

refactor code to handle sync_client_geometry_add

There was a potential bug for handling tizen_position_set request if the ec is under
pending_geometry.
We refactored code handling sync_geometry_set to compare the buffer size not serial.
For this, if the tizen_position_set was called under pending geometry, then we called
e_comp_wl_commit_sync_client_geometry_add with size(0x0).
In this case, the client could not send the buffer chagne event for size(0x0), so the
tizen_position_set request remained not to handled.

To resolve this, we refactor the e_comp_wl_commit_sync_client_geometry_add function.

Change-Id: Ib36eec68b918a5ebacbb192037a9dc4a082137a0