ARM: dts: imx7s: Fix CSI clocks

ARM: dts: imx7s: Fix CSI clocks

Per nxp,imx7-csi.yaml, there is only one CSI clock entry.

Fix it.

This fixes the following schema warnings:

imx7d-zii-rpu2.dtb: csi@30710000: clocks: [[1, 413], [1, 326], [1, 413]] is too long
	from schema $id: http://devicetree.org/schemas/media/nxp,imx7-csi.yaml#
imx7d-zii-rpu2.dtb: csi@30710000: clock-names:0: 'mclk' was expected
	from schema $id: http://devicetree.org/schemas/media/nxp,imx7-csi.yaml#
imx7d-zii-rpu2.dtb: csi@30710000: clock-names: ['axi', 'mclk', 'dcic'] is too long
	from schema $id: http://devicetree.org/schemas/media/nxp,imx7-csi.yaml#

Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>