armv8: ls2080a: Increase env sector size for qspi boot

Increase env sector size from 64kb to 256kb for qspi boot.

Signed-off-by: Santan Kumar <santan.kumar@nxp.com>
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>