/proc/pid/smaps: add mseal info for vma

Add sl in /proc/pid/smaps to indicate vma is sealed

Link: https://lkml.kernel.org/r/20240614232014.806352-2-jeffxu@google.com
Fixes: 8be7258aad ("mseal: add mseal syscall")
Signed-off-by: Jeff Xu <jeffxu@chromium.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jorge Lucangeli Obes <jorgelo@chromium.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Röttger <sroettger@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/filesystems/proc.rst

@@ -571,6 +571,7 @@ encoded manner. The codes are the following:
     um    userfaultfd missing tracking
     uw    userfaultfd wr-protect tracking
     ss    shadow stack page
+    sl    sealed
     ==    =======================================
 
 Note that there is no guarantee that every flag and associated mnemonic will