Hello Rik,
There is not a bare board SDK for the i.MX6UL (there was one for the i.MX6SL/S/D/Q which is no longer supported but that can be requested through a support case).
As for a CMSIS pack for IAR, IAR supports several NXP processors but I would need to ask you to contact them directly for more information on available tools.
https://www.iar.com/iar-embedded-workbench/partners/nxp/downloads-for-nxp-kits/
I hope this helps!
Regards,
