MLBEDSW-9441: Add default system configs and memory modes to Ethos-U85

 - Changed default CLI behaviour of Ethos-U85 to be consistent with
Ethos-U55 and Ethos-U65
 - Changed default config values to be read from the default configuration
file Arm/vela.ini rather than being hard coded

Change-Id: I28df5513d091cca87f85f381f97173c9baa3e3eb
Signed-off-by: Tim Hall <tim.hall@arm.com>