SECURE BOOT: Add command for validation of images

SECURE BOOT: Add command for validation of images

1. esbc_validate command is meant for validating header and
   signature of images (Boot Script and ESBC uboot client).
   SHA-256 and RSA operations are performed using SEC block in HW.
   This command works on both PBL based and Non PBL based Freescale
   platforms.
   Command usage:
   esbc_validate img_hdr_addr [pub_key_hash]
2. ESBC uboot client can be linux. Additionally, rootfs and device
   tree blob can also be signed.
3. In the event of header or signature failure in validation,
   ITS and ITF bits determine further course of action.
4. In case of soft failure, appropriate error is dumped on console.
5. In case of hard failure, SoC is issued RESET REQUEST after
   dumping error on the console.
6. KEY REVOCATION Feature:
   QorIQ platforms like B4/T4 have support of srk key table and key
   revocation in ISBC code in Silicon.
   The srk key table allows the user to have a key table with multiple
   keys and revoke any key in case of particular key gets compromised.
   In case the ISBC code uses the key revocation and srk key table to
   verify the u-boot code, the subsequent chain of trust should also
   use the same.
6. ISBC KEY EXTENSION Feature:
   This feature allows large number of keys to be used for esbc validation
   of images. A set of public keys is being signed and validated by ISBC
   which can be further used for esbc validation of images.

Signed-off-by: Ruchika Gupta <ruchika.gupta@freescale.com>
Signed-off-by: Gaurav Rana <gaurav.rana@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>