arm: armv8: Fix spl recover data section broken

arm: armv8: Fix spl recover data section broken

SPL recover data section is broken which causes reboot failure on
some i.MX platforms (iMX8QM/iMX95).
The global variable cold_reboot_flag is assigned to weak reset_flag
function which always return 1, so restore never been executed in
warm reboot.

Fixes: 1c37e59bfbba ("arm: armv8: Improve SPL data save and restore implementation")
Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>