ANDROID: Add symbol of _proc_mkdir

Pixel LTS work patch, commit 6ccab11c ("proc: fix
lookup in /proc/net subdirectories after setns(2)"),
export new symbol of `_proc_mkdir` in sctp.ko.
Update symbol list and update ABI XML file.

Leaf changes summary: 1 artifact changed
Changed leaf types summary: 0 leaf type changed
Removed/Changed/Added functions summary: 0 Removed, 0 Changed, 1 Added function
Removed/Changed/Added variables summary: 0 Removed, 0 Changed, 0 Added variable

1 Added function:

  [A] 'function proc_dir_entry* _proc_mkdir(const char*, umode_t, proc_dir_entry*, void*, bool)'

Bug: 180663378
Signed-off-by: Lucas Wei <lucaswei@google.com>
Change-Id: Id13e9816d4196fb43167b0e73dadf74d90c1967e