Implement the secinfo operation.

(Thanks to Usha Ketineni wrote an earlier version of this support.)

Cc: Usha Ketineni <uketinen@us.ibm.com>
Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>