arm: ls1021atwr: Add SD secure boot target

arm: ls1021atwr: Add SD secure boot target

Add SD secure boot target for ls1021atwr.
Implement board specific spl_board_init() to setup CAAM stream ID and
corresponding stream ID in SMMU. Change the u-boot size defined by a
macro for copying the main U-Boot by SPL to also include the u-boot
Secure Boot header size as header is appended to u-boot image. So header
will also be copied from SD to DDR.

Reviewed-by: Aneesh Bansal <[email protected]>
Signed-off-by: Sumit Garg <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Reviewed-by: York Sun <[email protected]>