Yes,I have got the solution from nxp local representive.
Below is how you can set the password to whatever you want with a few commands:
1. Stop at u-Boot stage by pressing any key after "Hit any key to stop autoboot" appears.
2. Modify the environment as specified below and boot:
=> setenv mmcroot /dev/mmcblk0p2 rootwait rw init=/bin/sh
=> boot
do _not_ issue "saveenv".
3. You will be presented a root shell without any authentication.
Use "passwd" command to set the password to whatever you want:
#/usr/bin/passwd vision
#sync
4. Powercycle the board.
5. When the system boots and comes to login, enter "vision" as username and the password you set.
