arm: dts: ls1028a-rdb: disable I2C buses 1 through 7

There is no I2C peripheral on these buses on the reference design board,
and the Linux device tree does not enable them either.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>