The register is set up with entries for SIENF and SIENR so you can call the functions available in the SDK like this,
Chip_PININT_SetPinModeEdge(LPC_PININT, PININTCH0); //Configure channel 0 interrupt as edge sensitive
Chip_PININT_EnableIntLow(LPC_PININT, PININTCH0); //Configure channel 0 interrupt falling edge interrupt
Chip_PININT_EnableIntHigh(LPC_PININT, PININTCH0); //Configure channel 0 interrupt rising edge interrupt
Chip_SYSCTL_SetPinInterrupt(0, 17); // Configure interrupt channel 0 for the GPIO pin 17 in SysCon block
Regards
Sanders7284