DCD check command is currently implemented for imximg v2 only.
This command may also be available for v1 as mentioned in IMX35RM as
DCD-address-type "wait/read", but due to the lack of further details
it will be not supported.
Signed-off-by: Alexander Kurz <akurz@blala.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>