arm64: dts: renesas: r8a77965: Remove stale reg property

Remove "reg" property from cache-controller-0 device node as it does not
have any unit address.

This silences the following DTC compiler warning:
Warning (unit_address_vs_reg): Node /cpus/cache-controller-0 has a reg
or ranges property, but no unit name

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>