OTA upgrade for smartlocker in i.MX7ULP kernel

[#1]

This package is a OTA upgrade implementation for smartlocker in i.MX7ULP kernel.

The bootaux command for i.MX7ULP can also be applied to other projects.

File description:

1. smartlocker OTA upgrade user manual.
2. Modified u-boot. Modification involves:
   1. Add bootaux command. To use this command, the M4 image will be read out from boot partition to TCM_L. (Or DDR and then it will be copied to TCM_L in the command)
      It took 19ms to read M4 image.
   2. Change u-boot default env. If M4 image and zImage read failed, recovery M4 image and zImage will be loaded.
3. patch of u-boot changes.
4. u-boot defconfig for bootaux change.
5. sh script, updater.sh.
6. Example for upgrade package.

7. Power shutdown in copying upgrade files may cause file broken. So currently, we use below copy strategy:

   1. Copy upgrade file to target directory as tmp file.

   2. Delete target file.

   3. Rename tmp file to target file.