as said, the mirroring of INTA and INTB does not require hardware connection.
Than you have to configure the chip:
- only one edge or both edge (with mcp23017 this is done choosing if rise an interrupt when the level is different from a value set or when it changes)
- active high or low
Remember that when an interrupt is found, the interrupt pin will output it and will not change its state until you read the gpio values!
i have not under hand my code, but it seems to me that it's possible to have interrupt working on mcp