conf: Add memory bandwidth allocation capability of host

Add new XML section to report host's memory bandwidth allocation
capability. The format as below example:

<host>
.....
<memory_bandwidth>
<node id='0' cpus='0-19'>
<control granularity='10' min ='10' maxAllocs='8'/>
</node>
</memory_bandwidth>
</host>

granularity ---- granularity of memory bandwidth, unit percentage.
min ---- minimum memory bandwidth allowed, unit percentage.
maxAllocs ---- maximum memory bandwidth allocation group supported.

Signed-off-by: Bing Niu <bing.niu@intel.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>