staging: lustre: reorder LOV_MAGIC_* definition

Since all the LOV_MAGIC_* definitions have the same
postfix values break that value out into its own
definition. With this we can check whether the magic's
postfix match the LOV_MAGIC_MAGIC or not: if yes,
then it is quite possible that the clients has
encountered an newer LOV magic. This extra information
can let us handle those cases more gracefully.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4941
Reviewed-on: http://review.whamcloud.com/10045
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>