debug_stream: Kconfig: Improve help message

Add reference to tools/debug_stream/debug_stream.py in the Kconfig
help message.

Signed-off-by: Jyri Sarha <jyri.sarha@linux.intel.com>

Author: Jyri Sarha

src/debug/debug_stream/Kconfig

@@ -7,7 +7,8 @@ config SOF_DEBUG_STREAM_SLOT
 	  information from SOF system that are streamed from SOF DSP
 	  to the host side for decoding and presentation. This option
 	  enables transferring the records from DSP to host over a
-	  debug window slot.
+	  debug window slot. To extract the debugstream see
+	  tools/debug_stream/debug_stream.py.
 
 if SOF_DEBUG_STREAM_SLOT