Revert "io_uring: drop any code related to SCM_RIGHTS"

This reverts commit a3812a47 which is
commit 6e5e6d27 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I84857293b288c8a160b2567d4018568c36893eff
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>