rename EB+MCF-EV123 to its current marketing name EB+CPU5282

* rename board directory to eb_cpu5282
* rename EB+MCF-EV123_.*config to eb_cpu5282_.*config
* add Maintainer for EB+CPU5282 board
* rename prompt

Signed-off-by: Jens Scharsig (BuS Elektronik) <esw@bus-elektronik.de>