ARM: dts: imx25: Fix the iim compatible string

[ Upstream commit f0b929f5 ]

Per imx-iim.yaml, the compatible string should only contain a single
entry.

Use it as "fsl,imx25-iim" to fix the following dt-schema warning:

imx25-karo-tx25.dtb: efuse@53ff0000: compatible: ['fsl,imx25-iim', 'fsl,imx27-iim'] is too long
	from schema $id: http://devicetree.org/schemas/nvmem/imx-iim.yaml#



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