Documentation/misc-devices/mei: Fix indentation of enumeration.

Properly indent a list in mei.txt in the same way as another list in
that file.

Reviewed-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Julian Brost <linux-kernel@0x4a42.net>
Signed-off-by: Fabian Hofmann <fabian.hofmann@fau.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>