How to make SirfStar IV chip operate as I2C slave only?
It does not look like this chip set supports talking to the chip as an I2C slave.

Page 22 of the A2235-H User manual shows all of the pin functions. 

Pins 17 and 18 are used as an I2C interface for the GPS module to talk to en external MEMs sensor for some level of IMU functionality.

Pins 14 and 22 are the I2C interface for the module to talk to a slave EEPROM device for saving non-volatile data, operating as a stand alone HOST MODE.

It looks like user communication with the GPS module is limited to the UART or SPI interfaces.