Revert "inet: inet_defrag: prevent sk release while still in use"

This reverts commit 9705f447 which is
commit 18685451 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: I9648d1fefa425994b1fc2a30153348e2b0f9e9bc
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>