ecore/wayland: Fix alpha windows on EGL backend.

ecore/wayland: Fix alpha windows on EGL backend.

Now the opaque and input regions are updated on ecore_wl_window_resize,
there's no need to call ecore_wl_window_buffer_attach() for this
anymore.

The checks on alpha and transparent flags were also fixed.

ecore_wl_window_update_size() is now called by ecore_wl_window_resize(),
reducing duplicated code.