vfio/spapr: use memseg walk instead of iteration
vfio/spapr: use memseg walk instead of iteration

Reduce dependency on internal details of EAL memory subsystem, and
simplify code.

Signed-off-by: Anatoly Burakov <814e00d8f6e4e81b7ccc7e3e5a0bfec0078f0203@intel.com>
Tested-by: Santosh Shukla <23b682afe3504ae4f88c66c3cabfb34f87e9916e@caviumnetworks.com>
Tested-by: Hemant Agrawal <90d96ef1ecd8ed49b97c7897be950e80824a9c5c@nxp.com>
Tested-by: Gowrishankar Muthukrishnan <b565c1cabbc104f9755b890159910f97e2efe01a@linux.vnet.ibm.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk