Commit 03b59bdb64e83e (paramter: The dev_add_param_*() return ERR_PTR(),
change no-ops to return ERR_PTR(-ENOSYS) instead of NULL) started using
ERR_PTR and errnos without including the relevant header.
This fixes the build for a lot of configurations.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>