arm64: dts: ls1028a-rdb: enable optee node

optee node was disabled by default, enabling it for ls1028a-rdb.

Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Sahil Malhotra <sahil.malhotra@nxp.com>
Acked-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>