Just force io_control to not accept turning the banks into multiple banks.

Author: Red-M

adafruit_mcp230xx/mcp23017.py

@@ -259,6 +259,8 @@ def io_control(self):
 
     @io_control.setter
     def io_control(self, val):
+        val |= 0b000001
+        val ^= 0b000001
         self._write_u8(_MCP23017_IOCON, val)
 
     @property

adafruit_mcp230xx/mcp23s17.py

@@ -263,6 +263,8 @@ def io_control(self):
 
     @io_control.setter
     def io_control(self, val):
+        val |= 0b000001
+        val ^= 0b000001
         self._write_u8(_MCP23S17_IOCON, val)
 
     @property