[Mesa-stable] cherry pick request for commit 87c3c9acd (st/dri: Use packed RGB formats)

[Ilia Mirkin]

I totally forgot to tag it with stable. Please add it in so that the
other nv30 changes have an effect.

Thanks,

  -ilia

commit 87c3c9acd29655d6c8778ea732f559eebeddd5f6
Author: Michel D<C3><A4>nzer <michel.daenzer at amd.com>
Date:   Mon Aug 10 18:44:18 2015 +0900

    st/dri: Use packed RGB formats

    Fixes Gallium based DRI drivers failing to load on big endian hosts
    because they can't find any matching fbconfigs.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=71789
    Signed-off-by: Michel D<C3><A4>nzer <michel.daenzer at amd.com>
    Reviewed-by: Marek Ol<C5><A1><C3><A1>k <marek.olsak at amd.com>
    Tested-by: Ilia Mirkin <imirkin at alum.mit.edu>