In SPDK, not all drivers are registered with DPDK at start up time. Previously, that meant DPDK always chose to set itself up in IOVA_PA mode. Instead, when the correct iova choice is unclear based on the devices and drivers known to DPDK at start up time, use other heuristics (such as whether /proc/self/pagemap is accessible) to make a better choice.
This enables SPDK to run as an unprivileged user again without requiring users to explicitly set the iova mode on the command line.
