ARM: dts: imx53-qsb-common: Fix 'led_gpio7_7@0' node with unit name and no reg property

The following build warning is seen with W=1:

Warning (unit_address_vs_reg): Node /soc/aips@50000000/iomuxc@53fa8000/imx53-qsb/led_gpio7_7@0 has a unit name, but no reg property

Fix this warning by removing '@0' from such node.

Signed-off-by: Marco Franchi <marco.franchi@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>