HID: hidraw: fix improper mutex release

Mutex can not be released unless all hid_device members are properly
initialized. Otherwise it would result in a race condition that can
cause NULL pointer kernel panic issue in hidraw_open where it uses
uninitialized 'list' member in list_add_tail().

Signed-off-by: Yonghua Zheng <younghua.zheng@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>