Do not hardcode paths in eglfs-brcm test.

Let the specs decide about egl headers and egl lib
location.

Fixes yocto RaspberryPi build without proper
egl support.

Change-Id: I4c8d655673aa0b2043bc376486cfe436afb93e42
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>