console: rename dpy_gl_scanout to dpy_gl_scanout_texture

We'll add a variant which accepts dmabufs soon.  Change
the name so we can easily disturgish the two variants.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 1487669841-13668-2-git-send-email-kraxel@redhat.com