mci: core: Check return value of dev_add_param_bool
Commit 03b59bd changed the
return values of dev_add_param_* to ERR_PTR(-ENOSYS) and broke a few boards.
We have now to care about the return value of dev_add_param_bool() in
mci_register().
Also set the ret variable when dev_add_param_bool() fails.
Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>