vfio/fsl-mc: Allow userspace to MMAP fsl-mc device MMIO regions

Allow userspace to mmap device regions for direct access of
fsl-mc devices.

Signed-off-by: Bharat Bhushan <Bharat.Bhushan@nxp.com>
Signed-off-by: Diana Craciun <diana.craciun@oss.nxp.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>