arm: ls1021a: Add QSPI or IFC support in SD boot for LS1021AQDS board

As QSPI and IFC are pin-multiplexed on LS1021A, only IFC is supported
in SD boot now. For the customer's demand, QSPI needs to be supported
in SD boot too.

This patch adds QSPI or IFC support in SD boot according to the
corresponding defconfig. For detail, ls1021aqds_sdcard_ifc_defconfig
is used to support IFC in SD boot and ls1021aqds_sdcard_qspi_defconfig
is used to support QSPI in SD boot.

Signed-off-by: Alison Wang <alison.wang@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>