docs: proc: update VmFlags documentation in smaps

Remove outdated VM_DENYWRITE("dw") reference and add missing
VM_LOCKONFAULT("lf") and VM_UFFD_MINOR("ui") flags.

[akpm@linux-foundation.org: add "dp" (VM_DROPPABLE), per Tal]
Link: https://lkml.kernel.org/r/20250607153614.81914-1-wangfushuai@baidu.com
Signed-off-by: wangfushuai <wangfushuai@baidu.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mariano Pache <npache@redhat.com>
Cc: xu xin <xu.xin16@zte.com.cn>
Cc: Tal Zussman <tz2294@columbia.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: wangfushuai

Documentation/filesystems/proc.rst

@@ -584,7 +584,6 @@ encoded manner. The codes are the following:
     ms    may share
     gd    stack segment growns down
     pf    pure PFN range
-    dw    disabled write to the mapped file
     lo    pages are locked in memory
     io    memory mapped I/O area
     sr    sequential read advise provided
@@ -607,8 +606,11 @@ encoded manner. The codes are the following:
     mt    arm64 MTE allocation tags are enabled
     um    userfaultfd missing tracking
     uw    userfaultfd wr-protect tracking
+    ui    userfaultfd minor fault
     ss    shadow/guarded control stack page
     sl    sealed
+    lf    lock on fault pages
+    dp    always lazily freeable mapping
     ==    =======================================
 
 Note that there is no guarantee that every flag and associated mnemonic will