doc: announce change to make DPDK IOVA aware

doc: announce change to make DPDK IOVA aware

When we run DPDK on guest or VFIO mode on host,
the dpdk library or device will not be directly accessing
the physical address. Instead, the device does go through
an IO address translation memory management unit. On x86,
we call it as IOMMU and on ARM as SMMU.

More details:
http://osidays.com/osidays/wp-content/uploads/2014/12/Final_OSI2014_IOMMU_DetailedView_Sanil_Anurup.pdf

Based on discussion in the following thread
http://dpdk.org/ml/archives/dev/2017-July/070850.html

We would like to change reference to physical address to more
appropriate name as with IOMMU/SMMU with
the device won't be dealing directly with the physical address.

An ABI change is planned for 17.11 to change following
data structure or functions to more appropriate name.
Currently planned to change it iova as instead of phys

Please note: The change will be only for the name and
functional aspects of the API will remain same.

Following functions/data structures name may change.
This list is based on v17.05-rc1. It may change based on v17.11 code base.

typedef:
phys_addr_t

structures:

struct rte_memseg::phys_addr
struct rte_mbuf::buf_physaddr

functions:
rte_mempool_populate_phys()
rte_mempool_populate_phys_tab()
rte_eal_using_phys_addrs()
rte_mem_virt2phy()
rte_dump_physmem_layout()
rte_eal_get_physmem_layout()
rte_eal_get_physmem_size()
rte_malloc_virt2phy()
rte_mem_phy2mch()

Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
Acked-by: Santosh Shukla <santosh.shukla@caviumnetworks.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Thomas Monjalon <thomas@monjalon.net>