overo.conf: add PREFERRED_PROVIDER for all gl-libs
overo.conf: add PREFERRED_PROVIDER for all gl-libs

Signed-off-by: Andreas Müller <d72a15aaaca3a7afa855175c72dc8d2e05931e32@googlemail.com>

schnitzeltony/meta-gumstix-community,schnitzeltony/meta-gumstix-community