Smack: Fix the bug smackcipso can't set CIPSO correctly

Bug report: https://tizendev.org/bugs/browse/TDIS-3891

The reason is userspace libsmack only use "smackfs/cipso2" long-label interface,
but the code's logical is still for orginal fixed length label. Now update
smack_cipso_apply() to support flexible label (<=256 including tailing '\0')

There is also a bug in kernel/security/smack/smackfs.c:
When smk_set_cipso() parsing the CIPSO setting from userspace, the offset of
CIPSO level should be "strlen(label)+1" instead of "strlen(label)"

Signed-off-by: Passion,Zhao <passion.zhao@intel.com>

security/smack/smackfs.c

@@ -881,7 +881,7 @@ static ssize_t smk_set_cipso(struct file *file, const char __user *buf,
 	if (format == SMK_FIXED24_FMT)
 		rule += SMK_LABELLEN;
 	else
-		rule += strlen(skp->smk_known);
+		rule += strlen(skp->smk_known) + 1;
 
 	ret = sscanf(rule, "%d", &maplevel);
 	if (ret != 1 || maplevel > SMACK_CIPSO_MAXLEVEL)