eal/linux: allow to map BARs with MSI-X tables

eal/linux: allow to map BARs with MSI-X tables

While VFIO doesn't allow us to map complete BARs with MSI-X tables,
it does allow us to map around them in PAGE_SIZE granularity. There
might be adapters that provide their registers in the same BAR
but on a different page. For example, Intel's NVME adapter, though
not a network adapter, provides only one MMIO BAR that contains
the MSI-X table.

Signed-off-by: Dan Aloni <dan@kernelim.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>