arm64: dts: lx2160a: update fspi node

Flash mt35xu512aba connected to FlexSPI controller supports
1-1-8/1-8-8 protocol.
Added flag spi-rx-bus-width and spi-tx-bus-width with values as
8 and 8 respectively for both flashes connected at CS0 and CS1.

Signed-off-by: Yogesh Narayan Gaur <yogeshnarayan.gaur@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>