staging: lustre: fiemap: set FIEMAP_EXTENT_LAST correctly

When we've collected enough extents as user requested, we'd check one
further to decide whether we've reached the last extent of the file.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5933
Reviewed-on: http://review.whamcloud.com/12781


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>