The man for xl.cfg have the "devtype=hostdev" option, but xl only
understand "type=hostdev", fix the manual to reflect actual
implementation.
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com> Reviewed-by: George Dunlap <george.dunlap@citrix.com> Acked-by: Wei Liu <wei.liu2@citrix.com>