imx: hab: Convert non-NULL IVT DCD pointer warning to an error

imx: hab: Convert non-NULL IVT DCD pointer warning to an error

The following NXP application notes and manual recommend to ensure the
IVT DCD pointer is Null prior to calling HAB API authenticate_image()
function:

- AN12263: HABv4 RVT Guidelines and Recommendations
- AN4581: Secure Boot on i.MX50, i.MX53, i.MX 6 and i.MX7 Series using
  HABv4
- CST docs: High Assurance Boot Version 4 Application Programming
  Interface Reference Manual

Commit ca89df7dd46f ("imx: hab: Convert DCD non-NULL error to warning")
converted DCD non-NULL error to warning due to the lack of documentation
at the time of first patch submission. We have warned U-Boot users since
v2018.03, and it makes sense now to follow the NXP recommendation to
ensure the IVT DCD pointer is Null.

DCD commands should only be present in the initial boot image loaded by
the SoC ROM. Starting in HAB v4.3.7 the HAB code  will generate an error
if a DCD pointer is present in an image being authenticated by calling the
HAB RVT API. Older versions of HAB will process and run DCD if it is
present, and this could lead to an incorrect authentication boot flow.

Signed-off-by: Breno Lima <breno.lima@nxp.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>