Hello ByeongHeon YOO,
The L4.1.15_2.0.1 repo was removed from what I see. This version of the BSP added some patches for i.MX6UL and i.MX7D.
I would suggest using L4.1.15_2.1.0. The instructions on how to setup this BPS are available on the release documentation on the link below (you may need to login to download this file)
L4.1.15_2.1.0_LINUX_DOCS
https://www.nxp.com/webapp/Download?colCode=L4.1.15_2.1.0_LINUX_DOCS
My apologies for the inconvenience! I hope this helps!
Regards,