package/cegui: disable OpenGLES renderer

package/cegui: disable OpenGLES renderer

Support of OpenGLES generates tons of autobuilders failures
so let's disable it till upstream finds a solution for that.

Fixes:
 http://autobuild.buildroot.net/results/41d/41d10c09472fbb8481a72c4f8bed789bb15bb3c2//
 http://autobuild.buildroot.net/results/9a8/9a8122b4d3d0aa9d71cdf8d21359411b130741f8//
 http://autobuild.buildroot.net/results/7e5/7e5dd79b48abde09bf4633b196579da5561f9fa1//

and many more...

Signed-off-by: Bartosz Bilas <b.bilas@grinn-global.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>