dmi-id: don't free dev structure after calling device_register

dmi_dev is freed in error exit code but, according to the document
of device_register, it should never directly free device structure
after calling this function, even if it returned an error! Use
put_device() instead.

Signed-off-by: Allen Hung <allen_hung@dell.com>
Signed-off-by: Jean Delvare <jdelvare@suse.de>