if wl2_input logic gets a 'touch down' event from touch device,
input->focus.touch has set and it cause the logic handles every input as touch input
from that moment at _ecore_wl2_input_mouse_move_send function.
that is the reason why the patch(410c1f95879e46a5e52132662d4c43b74e95a251) has written for.
however, if there are multiple touch input devices,
clearing focus.touch variable without checking any conditions causes another problem.
I mean a case such as 'touch 1 down' -> 'touch 2 down' -> 'touch 1 up' -> 'touch 2 up'
at the moment 'touch 1 up' event executed, focus.touch would be cleared,
and 'touch 2 up' and following touch events will not be executed properly at the moment.
this patch counts a number of touch devices which are grabbing to clear focus.touch at proper time.