struct cdit_header was never used across any of the amd drivers nor
this is exposed to UAPI so it can be removed.
This patch removes struct cdit_header and refactor code accordingly
Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com> Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com> Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>