intel_th: gth: Handle host mode correctly

intel_th: gth: Handle host mode correctly

When detecting host debugger mode either though a module option or via
the scratchpad register, do not export any configuration or capture
related attributes to userspace and refuse attempts by the output drivers
to configure output ports.

This way, GTH can still act as a hub and ensure that the other components
that rely on its presence continue to function properly, namely the
source devices.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>