fusee/exo: support dynamic control of invert flag for logging

config_templates/exosphere.ini

@@ -43,6 +43,9 @@
 #  Desc: Controls the baud rate exosphere will set up for logging.
 #  NOTE: 0 is treated as equivalent to 115200.
 
+# Key: log_inverted, default: 0.
+#  Desc: Controls whether the logging uart port is inverted.
+
 [exosphere]
 debugmode=1
 debugmode_user=0
@@ -53,3 +56,4 @@ blank_prodinfo_emummc=0
 allow_writing_to_cal_sysmmc=0
 log_port=0
 log_baud_rate=115200
+log_inverted=0