The VFIO section of the page about Linux drivers was rather long and
unstructured. This can be improved by splitting it up into subsections,
to cover the specifics of memory limits and creating VFs. When moving
the various text notes into the relevant subsections, we can drop the
note about kernels earlier than 3.6, since DPDK no longer supports
kernels that old.
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>