armv8: fsl-layerscape: avoid DT fixup warning

armv8: fsl-layerscape: avoid DT fixup warning

sec_firmware reserves JR3 for it's own usage and deletes the JR3 node
from the device tree. This causes this warning to be issued when doing
the device tree fixup:

WARNING could not find node fsl,sec-v4.0-job-ring: FDT_ERR_NOTFOUND.

Fix it by excluding the device tree fixup for the JR reserved by
sec_firmware.

Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Reviewed-by: Horia Geanta <horia.geanta@nxp.com>
Reviewed-by: Bharat Bhushan <bharat.bhushan@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>