stm class: make config_item_type const

Make config_item_type structures const as they are either passed to a
function having the argument as const or used inside a if statement or
stored in the const "ci_type" field of a config_item structure.

Done using Coccinelle.

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>