memzone: enable IOVA-contiguous reserving

memzone: enable IOVA-contiguous reserving

This adds a new flag to request reserved memzone to be IOVA
contiguous. This is useful for allocating hardware resources like
NIC rings/queues etc.For now, hugepage memory is always contiguous,
but we need to prepare the drivers for the switch.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Tested-by: Santosh Shukla <santosh.shukla@caviumnetworks.com>
Tested-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Tested-by: Gowrishankar Muthukrishnan <gowrishankar.m@linux.vnet.ibm.com>