Hello, @Kimi
Thanks for your reply.
I am able to understand the status, when building BSP44, the DDR FW are required during the Yocto building.
You are obtain the FW images from your NXP account, and get them via the following way:

While downloaded, extracted it to find the images

At last, modify the conf/local.conf following the guide from BSP44 UM, and then rebuild the BSP.

I hope it will help.
BR
Chenyin