staging: ramster: Add incremental accessory counters

Add incremental accessory counters that are going to be used for
debug fs entries.

Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>