gpu/hwdec: reorder `drmprime` below `drmprime_drm`

The older overlay based drmprime hwdec should be preferred to the new
texture mapping one. This is for a few reasons:

1. In any situation where both hwdecs work, it's probably right to use
   the more mature one by default, for now.
2. It seems like the overlay path primarily works on older SoCs
   where the texture path is less performant, and in at least one
   tested case is visually buggy, so you definitely want it to be
   tried first.
3. In situations where the old hwdec doesn't work, it will fall through
   to the new one.

video/out/gpu/hwdec.c

@@ -75,8 +75,8 @@ const struct ra_hwdec_driver *const ra_hwdec_drivers[] = {
     &ra_hwdec_rpi_overlay,
 #endif
 #if HAVE_DRM
-    &ra_hwdec_drmprime,
     &ra_hwdec_drmprime_drm,
+    &ra_hwdec_drmprime,
 #endif
 
     NULL