Hi,
What is the revision of silicon on your custom board. PG 1.0 is impacted by Advisory 8 which could lead to boot related issues due to incorrect initialization of PLLs. The value latched into DEVSTAT register appears to be correct.
Can please run the debug GEL file provided here and provide us the log when the device boot fails. Ensure that you don`t use any gel file when you connect to the device initially after the boot fails then load and run the debug GEL script. It is important for us to understand the value of the Program counter and the state of the device when the boot fails to understand when the failure occurs.Also let us know if you see SPI transactions on the SPI lines after you power on the device?
Regards,
Rahul
PS: Debug GEL file is provided on the wiki page below under debug section:
http://processors.wiki.ti.com/index.php/Keystone_Device_Architecture