config: move image field to hafnium-base
Follow up to: a502ce34 feature: add an optional 'image' field to config files. 0ca0537d config: ffa-hafnium-optee: Use the optional 'image' field
Move the "image:" field to hafnium-base config and remove it from cca-4world and ffa-hafnium-optee configs.
This will benefit configurations consuming hafnium-base config including above ones and ffa-tftf, or future configuration consuming this config.
Signed-off-by: Olivier Deprez olivier.deprez@arm.com