vo: hwdec: prioritise drmprime over drmprime_overlay

I originally left `drmprime_overlay` as higher priority because
`drmprime` was new, and because I didn't have any hardware where both
worked (only one or the other) so I couldn't compare relative
performance, and if only one worked, the priority didn't matter.

But with time and more usage, we've reached a point where we can say we
would recommend using `drmprime` in situations where both work, and
we've also been able to identify hardware where both do indeed work and
it seems that `drmprime` is more reliable.

So, let's flip them.

video/out/gpu/hwdec.c

@@ -74,8 +74,8 @@ const struct ra_hwdec_driver *const ra_hwdec_drivers[] = {
     &ra_hwdec_rpi_overlay,
 #endif
 #if HAVE_DRM
-    &ra_hwdec_drmprime_overlay,
     &ra_hwdec_drmprime,
+    &ra_hwdec_drmprime_overlay,
 #endif
 #if HAVE_ANDROID_MEDIA_NDK
     &ra_hwdec_aimagereader,