The DeviceTree Specification v0.3 specifies that the cache node
'cache-level' property is 'required'.  Cf. s3.8 Multi-level and Shared
Cache Nodes.

Update the Device Trees accordingly.
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Link: https://lore.kernel.org/r/20221107155825.1644604-19-pierre.gondois@arm.com
[geert: Update description]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>