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

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)"

Change-Id: I7be85b4ade557e25569970e61c9e09ca01b5f2d9
Signed-off-by: Passion,Zhao <passion.zhao@intel.com>
Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>