vfio/common: Fix wrong %m usages

vfio/common: Fix wrong %m usages

There are several places where the %m conversion is used if one of
vfio_dma_map(), vfio_dma_unmap() or vfio_get_dirty_bitmap() fail.

The %m usage in these places is wrong since %m relies on errno value while
the above functions don't report errors via errno.

Fix it by using strerror() with the returned value instead.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20230307125450.62409-3-joao.m.martins@oracle.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>