ecore-drm: Add logical pointer x, y variable in seat for reflecting multiple pointer...

ecore-drm: Add logical pointer x, y variable in seat for reflecting multiple pointer's movement

Summary: When one pointer moves, we should update the position of other devices.

Test Plan:
(1) Two pointer devices are connected.
(2) Move the cursor to (x, y) position using "device 1".
(3) When you move the cursor using "device 2", the cursor doesn't start from (x, y) position. This causes discontinuous mouse motion.

Reviewers: raster, zmike, gwanglim, stefan_schmidt, devilhorns, ManMower

Reviewed By: devilhorns, ManMower

Subscribers: cedric, Jeon, input.hacker, jpeg

Differential Revision: https://phab.enlightenment.org/D3384