UPSTREAM: Make anon_inodes unconditional

Make the anon_inodes facility unconditional so that it can be used by core
VFS code.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

(cherry picked from commit dadd2299ab61fc2b55b95b7b3a8f674cdd3b69c9)

Bug: 135608568
Test: test program using syscall(__NR_sys_pidfd_open,..) and poll()
Change-Id: I2f97bda4f360d8d05bbb603de839717b3d8067ae
Signed-off-by: Suren Baghdasaryan <surenb@google.com>