Revert "wl_egl: add exception checking to find invalid wl_egl_buffer"

Revert "wl_egl: add exception checking to find invalid wl_egl_buffer"

This reverts commit c74b4ab60aa2a82a66b01fac6125af0566fc73da.
 - That exception check doesn't protected with wl_egl_surface->buffers_mutex.
 - _thread_wl_surface_commit function is called inside of wl_egl_buffer->mutex is locked.
 - It means wl_egl_buffer is available when _thread_wl_surface_commit is called.
 - If wl_egl_surface->buffers_mutex is used inside of wl_egl_buffer->mutex then deadlock will be occurred.

Change-Id: I688f963827590f045bd3f97a7d6298e5281fb6e1