ls1021a: QSPI: update the node for QSPI support

Add the name for register space and memory space.
<0x1550000 0x10000 > is the QSPI register space.
<0x40000000 0x4000000> is the QSPI memory space.

Signed-off-by: Yuan Yao <yao.yuan@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>