ARM: dts: ls1021a: Add support for QSPI with ls1021a SoC

Add QSPI node support, and this function is disabled by default
This setting could be overwritten in board-level definitions

Signed-off-by: SZ Lin <sz.lin@moxa.com>
Acked-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>