mesa: enable dri in native/nativesdk through gallium drivers

Previously, dri was enabled via a token dri driver (swrast, then
nouveau). Upstream is discussing removing dri drivers altogether
(they're becoming difficult to support and only needed for obsolete
x86 hardware), so let's prepare for that happening in the future:

https://lists.freedesktop.org/archives/mesa-dev/2021-March/224984.html



Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>