serialhdl: Calculate baudadjust from MCU's baud instead of host baud

Store the baud rate the MCU is configured for in the "identify" data
and use that rate when calculating the baudadjust parameter.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

scripts/buildcommands.py

@@ -153,7 +153,7 @@ def build_identify(cmd_by_id, msg_to_id, responses, static_strings
     data['commands'] = sorted(cmd_by_id.keys())
     data['responses'] = sorted(responses)
     data['static_strings'] = static_strings
-    configlist = ['MCU', 'CLOCK_FREQ']
+    configlist = ['MCU', 'CLOCK_FREQ', 'SERIAL_BAUD']
     data['config'] = dict((i, config['CONFIG_'+i]) for i in configlist
                           if 'CONFIG_'+i in config)
     data['version'] = version