LU-13717 sec: missing defs in includes for client encryption

LU-13717 sec: missing defs in includes for client encryption

Add a few missing definitions in lustre_crypto.h that are required
in case Lustre client encryption is built against the in-kernel
fscrypt library.

Fixes: 028281ae19 ("LU-13717 sec: rework includes for client encryption")
Test-Parameters: trivial
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I1965503554dcf660770d201444cfafd54aa84dce
Reviewed-on: https://review.whamcloud.com/45221
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>