imx: imx8: bootaux: Add i.MX8 M4 boot support

1. Implement bootaux for the M4 boot on i.MX8QM and QXP. Users need to download
   M4 image to any DDR address first. Then use the
   "bootaux <M4 download DDR address> [M4 core id]" to boot CM4_0
   or CM4_1, the default core id is 0 for CM4_0.

   Since current M4 only supports running in TCM. The bootaux will copy
   the M4 image from DDR to its TCML.

2. Implment bootaux for HIFI on QXP
   command: bootaux 0x81000000 1

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>