firmware: vpd: avoid potential use-after-free when destroying section

We should not free info->key before we remove sysfs attribute that uses
this data as its name.

Fixes: 049a59db ("firmware: Google VPD sysfs driver")
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>