Since the functionality is more or less identical to
EGL_MESA_platform_surfaceless, the test with a copy of it.

Changes, as listed in the test itself, include:
 - s/MESA_platform_surfaceless/EXT_platform_device/g
 - entrypoint handling - eglQueryDeviceStringEXT, eglQueryDevicesEXT
and eglGetPlatformDisplayEXT
 - custom GetDisplay, based on eglQueryDevicesEXT
 - couple of s/PIGLIT_SKIP/PIGLIT_FAIL/

v2: Use eglQueryDeviceStringEXT to get a DRM backed device (Mathias)
v3: PIGLIT_SKIP when missing a DRM device in get_device_display (Mathias)
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Mathias Fröhlich <mathias.froehlich@web.de>