arm: dts: lx2160a: Use flexspi in octal I/O mode

Configure RX and TX bus-width values to use flexspi in octal I/O mode.
If bus-widths are not specified, then single I/O mode is set by default.

Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>