hw/smbios: Fix leaked fd in save_opt_one() error path

hw/smbios: Fix leaked fd in save_opt_one() error path

Fix the following Coverity issue (RESOURCE_LEAK):

  CID 1432879: Resource leak

    Handle variable fd going out of scope leaks the handle.

Replace a close() call by qemu_close() since the handle is
opened with qemu_open().

Fixes: bb99f4772f5 ("hw/smbios: support loading OEM strings values from a file")
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20201030152742.1553968-1-philmd@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>