Hi Bikash,
Please be careful read the mention file. You will see:
static void __init am335x_evm_init(void)
{
am33xx_cpuidle_init();
am33xx_mux_init(board_mux);
......
see the board_mux structure and follow the initialization. Do you have the touchscreen driver? If you have you can point the driver initialization there.
BR
Ivan
BR
Ivan