base: dd: fix error return code of driver_sysfs_add()

base: dd: fix error return code of driver_sysfs_add()

When device_create_file() fails and returns a non-zero value,
no error return code of driver_sysfs_add() is assigned.
To fix this bug, ret is assigned with the return value of
device_create_file(), and then ret is checked.

Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Link: https://lore.kernel.org/r/20210324023405.12465-1-baijiaju1990@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>