Add QSPI node in dtsi(ls1088a), and dts(ls1088ardb, ls1088aqds) boards.

Both ls1088ardb and ls1088aqds has two 64MB flash from SPANSION(s25fs512s).
QUAD I/O is tested in case of read and single I/O is tested in case of
write.
Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
Signed-off-by: Ashish Kumar <Ashish.Kumar@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>