The following dtc warning is seen when building with W=1:

arch/arm/boot/dts/imx6q-prtwd2.dts:33.8-43.4: Warning (unit_address_vs_reg): /i2c@4: node has a unit name, but no reg or ranges property

Remove the unneeded i2c unit name to fix the issue.

Fixes: 88010b81 ("ARM: dts: add Protonic WD2 board")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>