egl_dri: rework dri extension handling

Use designated initialisers, and store the extensions pointers as const.

The loader extensions __DRIdri2LoaderExtension and __DRIswrastLoaderExtension
are setup by the platform backends so they should not be constified.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
2 files changed