vhost: add power monitor API

vhost: add power monitor API

This commit defines rte_vhost_power_monitor_cond which is used to pass
some information to vhost driver. The information is including the
address to monitor, the expected value, the mask to extract value read
from 'addr', the value size of monitor address, the match flag used to
distinguish the value used to match something or not match something.

Vhost driver can use these information to fill rte_power_monitor_cond.

Signed-off-by: Miao Li <miao.li@intel.com>
Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
Acked-by: David Hunt <david.hunt@intel.com>