The mentioned approach was tested several years ago and described in the AN12081 - RAM Boot using CodeWarrior on LS1046ARDB.Please note that QorIQ SDK v2.0-1703 was used during the testing and bootloader initialization was based on PPA firmware which is not supported in the modern SDK (was replaced by TF-A).
Considering above, it is more straightforward to use CodeWarrior Flash Programmer to write firmware into the on-board SPI Flash. Refer to the CodeWarrior Development Studio for QorIQ LS series - ARM V8 ISA, Targeting Manual, 9.4 Board recovery in case of missing/corrupt RCW in IFC memory.