armv8: LS1088A_QSPI: SECURE_BOOT: Images validation

armv8: LS1088A_QSPI: SECURE_BOOT: Images validation

Validates PPA, MC, DPC, Bootscript, DPL and Kernel images in ESBC
phase using esbc_validate command.

Enable validation of boot.scr script prior to its execution dependent
on "secureboot" flag in environment

Add header address for PPA to be validated during ESBC phase for
LS1088A platform based on LAyerscape Chasis 3.

Moves sec_init prior to ppa_init as for validation of PPA sec must
be initialised before the PPA is initialised.

Signed-off-by: Udit Agarwal <[email protected]>
Signed-off-by: Vinitha Pillai-B57223 <[email protected]>
Signed-off-by: Sumit Garg <[email protected]>
Reviewed-by: York Sun <[email protected]>