crypto: jitter - Use kvfree_sensitive() to fix Coccinelle warning

Replace memzero_explicit() and kvfree() with kvfree_sensitive() to fix
the following Coccinelle/coccicheck warning reported by
kfree_sensitive.cocci:

	WARNING opportunity for kfree_sensitive/kvfree_sensitive

Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>