arm64: dts: ls1012a: Add QSPI node properties

Add support for QSPI on NXP layerscape LS1012A-RDB, LS1012A-QDS,
LS1012A-FRDM and LS1012A-FRWY boards.

LS1012A-RDB has 2 Spansion "s25fs512s" flashes of size 64M each and only
one can be accessed at a time.
LS1012A-QDS/FRDM has 1 spansion "s25fs512s" flash of size 64M.
LS1012A-FRWY has one winbond "w25q16dw" flash of size 2M.

Use generic compatibles as "jedec,spi-nor" for automatic detection of
flash. Configure RX and TX buswidth values as 2 as only two I/O lines are
available for data transfer.

Add ls1012a(si) node alongwith flash nodes.

Signed-off-by: Ashish Kumar <Ashish.kumar@nxp.com>
Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>