ARM: dts: exynos: Align L2 cache-controller nodename with dtschema

Fix dtschema warning message by changing nodename to 'cache-controller':

    DT_SCHEMA_FILES=Documentation/devicetree/bindings/arm/l2c2x0.yaml
    arch/arm/boot/dts/exynos4210-i9100.dt.yaml: l2-cache-controller@10502000:
	$nodename:0: 'l2-cache-controller@10502000' does not match '
	^(cache-controller|cpu)(@[0-9a-f,]+)*$'

Signed-off-by: Anand Moon <linux.amoon@gmail.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>