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

[ Upstream commit 69cc1502 ]

Fix dtschema validator warnings like:
    l2-cache@a02000: $nodename:0:
        'l2-cache@a02000' does not match '^(cache-controller|cpu)(@[0-9a-f,]+)*$'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Stable-dep-of: ee70b908 ("ARM: dts: nxp/imx6sll: fix wrong property name in usbphy node")
Signed-off-by: Sasha Levin <sashal@kernel.org>