ASoC: topology: Disable use from userspace

Since the topology API is still in sufficient flux for changes to be
identified disable the use of the userspace ABI by adding #error
statements to the code, ensuring that nobody relies on the headers as
currently defined.  It is expected that this change will be reverted for
v4.3.

Signed-off-by: Mark Brown <broonie@kernel.org>

include/uapi/sound/asoc.h

@@ -18,6 +18,12 @@
 #include <linux/types.h>
 #include <sound/asound.h>
 
+#ifndef __KERNEL__
+#error This API is an early revision and not enabled in the current
+#error kernel release, it will be enabled in a future kernel version
+#error with incompatible changes to what is here.
+#endif
+
 /*
  * Maximum number of channels topology kcontrol can represent.
  */