mpc85xx: convert WS-AP3710i to simpleImage wrapper

mpc85xx: convert WS-AP3710i to simpleImage wrapper

Convert the Enterasys WS-AP3710i access point to use the simpleImage
wrapper.

This is necessary, as the bootlaoder does not align the DTB correctly
(and does not support altering the FDT loadaddress). Booting images with
kernels 5.15 and later can break depending on the alignment on the DTB
within the FIT image.

Signed-off-by: David Bauer <mail@david-bauer.net>