intel_th: Support Host Debugger mode of operation

intel_th: Support Host Debugger mode of operation

This patch adds a 'host_mode' module option to enable host-driven
operational mode in the driver. In this mode, the driver does not
perform trace configuration or enable trace capture, but still
provides all the means necessary for software trace sources to
write their data to the Trace Hub. This means that the debug host
takes care of all the configuration and enabling and we do not
interfere.

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