ARM: dts: imx51-ts4800: Fix 'port@0' node with unit name and no reg property

The following build warning is seen with W=1:

Warning (unit_address_vs_reg): Node /display-di0/port@0 has a unit name,
but no reg property

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

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