tools: debug_stream.py: Cut text msg when first '\0' is encountered

The utf-8 decoder does not appear to be sensitive to '\0' in the
buffer so cut from word boundary may produce unwanted characters at
the end of the message.

Make also the text message always star from the beginning of the line
and not from the same line with "CPU X:" tag.

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

Author: Jyri Sarha

tools/debug_stream/debug_stream.py

@@ -162,8 +162,9 @@ def print_text_msg(self, record, cpu):
         buffer = (
             ctypes.c_ubyte * (len(record) - ctypes.sizeof(TextMsg))
         ).from_address(ctypes.addressof(record) + ctypes.sizeof(TextMsg))
-        msg = bytearray(buffer).decode("utf-8")
-        print("CPU %u: %s" % (cpu, msg))
+        payload = bytes(buffer)
+        msg = payload.split(b"\0", 1)[0].decode("utf-8", errors="replace")
+        print("CPU %u:\n%s" % (cpu, msg))
         return True
 
 class DebugStreamSectionDescriptor(ctypes.Structure):