Remove widgets dependency from eglfs

Remove widgets dependency from eglfs

eglfs uses the (old) OpenGL paint engine for paint operations. This drags in a
QWidget dependency and hence everything bar the kitchen sink. This change
gets eglfs buildable without widget support although anything which relies
on a QPaintDevice will end up rendering nothing to the screen. (Similar
to the QWS simplegl driver)

Change-Id: If7fcdb79038ef7568e771402fd1667bc0318ff5f
Reviewed-by: Jørgen Lind <jorgen.lind@nokia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>