dt-bindings: mips: mips-cm: Add a new compatible string for EyeQ6

The CM3.5 used on EyeQ6 reports that Hardware Cache Initialization is
complete, but in reality it's not the case. It also incorrectly
indicates that Hardware Cache Initialization is supported. This new
compatible string allows warning about this broken feature that cannot
be detected at runtime.

Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>