imx: hab: Convert DCD non-NULL error to warning

commit 8c4037a0 ("imx: hab: Ensure the IVT DCD pointer is Null prior
to calling HAB authenticate function.") makes the DCD field being NULL a
dependency.

This change though will break loading and executing of existing pre-signed
binaries on a u-boot update i.e. if this change is deployed on a board you
will be forced to redo all images on that board to NULL out the DCD.

There is no prior guidance from NXP that the DCD must be NULL similarly
public guidance on usage of the HAB doesn't call out this NULL dependency
(see boundary devices link).

Since later SoCs will reject a non-NULL DCD there's no reason to make a
NULL DCD a requirement, however if there is an actual dependency for later
SoCs the appropriate fix would be to do SoC version checking.

Earlier SoCs are capable (and happy) to authenticate images with non-NULL
DCDs, we should not be forcing this change on downstream users -
particularly if it means those users now must rewrite their build systems
and/or redeploy signed images in the field.

Fixes: 8c4037a0 ("imx: hab: Ensure the IVT DCD pointer is Null prior
to calling HAB authenticate function.")

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: Utkarsh Gupta <utkarsh.gupta@nxp.com>
Cc: Breno Lima <breno.lima@nxp.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Link: https://boundarydevices.com/high-assurance-boot-hab-dummies


Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>