tools: L2 CAT: support show cbm for L2 CAT.

tools: L2 CAT: support show cbm for L2 CAT.

This patch implements changes in xl/xc changes to support
showing CBM of L2 CAT.

The new level option is introduced to original CAT showing
command in order to show CBM for specified level CAT.
- 'xl psr-cat-show' is updated to show CBM of a domain
  according to input cache level.

Examples:
root@:~$ xl psr-cat-show -l2 1
Socket ID       : 0
Default CBM     : 0xff
   ID                     NAME             CBM
    1                 ubuntu14            0x7f

Signed-off-by: He Chen <he.chen@linux.intel.com>
Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>