MLK-20061-1: doc: imx: habv4: Add Encrypted Boot documentation for i.MX 6 and i.MX 7 family devices

Add useful documentation for encrypted boot:
- Add 2 CSF examples for encrypt and sign
- How to encrypt and sign a U-Boot binary on closed device
- Why and how increase the PRIBLOB bitfield from CAAM SCFGR

Signed-off-by: Clement Le Marquis <clement.lemarquis@nxp.com>
(cherry picked from commit 3732dddfeddd989ca1fb930972f19303e3b67756)
3 files changed