freedreno/a6xx: Enable FMT6_10_10_10_2_UNORM blitting

Now that we correctly program the _DEST version for the blit
destination and use float16 internal format, these formats work with
the blitter.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5717>

src/gallium/drivers/freedreno/a6xx/fd6_blitter.c

@@ -148,9 +148,6 @@ ok_format(enum pipe_format pfmt)
 	if (fmt == FMT6_NONE)
 		return false;
 
-	if (fmt == FMT6_10_10_10_2_UNORM_DEST)
-		return false;
-
 	return true;
 }