spl: nand: sunxi: stop guessing the redundant u-boot offset

Use CONFIG_SYS_NAND_U_BOOT_OFFS_REDUND value instead of trying to guess
where the redundant u-boot image is based on simple (and most of the time
erroneous) heuristics.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>

# Conflicts:
#	drivers/mtd/nand/sunxi_nand_spl.c
1 file changed