ARM: dts: imx6dl: Remove unneeded label and unit address

Remove unneeded label and unit address in order to fix the following
build warnings with W=1:

arch/arm/boot/dts/imx6dl-apf6dev.dtb: Warning (unit_address_vs_reg): Node /soc/aips-bus@2000000/iomuxc-gpr@20e0000/ipu1_csi0_mux@34 has a unit name, but no reg property
arch/arm/boot/dts/imx6dl-apf6dev.dtb: Warning (unit_address_vs_reg): Node /soc/aips-bus@2000000/iomuxc-gpr@20e0000/ipu1_csi1_mux@34 has a unit name, but no

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>