remove most callers of kernel_setsockopt v3

From: Christoph Hellwig
Date: Thu May 28 2020 - 01:17:25 EST

Hi Dave,

this series removes most callers of the kernel_setsockopt functions, and
instead switches their users to small functions that implement setting a
sockopt directly using a normal kernel function call with type safety and
all the other benefits of not having a function call.

In some cases these functions seem pretty heavy handed as they do
a lock_sock even for just setting a single variable, but this mirrors
the real setsockopt implementation unlike a few drivers that just set
set the fields directly.

Changes since v2:
- drop the separately merged kernel_getopt_removal
- drop the sctp patches, as there is conflicting cleanup going on
- add an additional ACK for the rxrpc changes

Changes since v1:
- use ->getname for sctp sockets in dlm
- add a new ->bind_add struct proto method for dlm/sctp
- switch the ipv6 and remaining sctp helpers to inline function so that
the ipv6 and sctp modules are not pulled in by any module that could
potentially use ipv6 or sctp connections
- remove arguments to various sock_* helpers that are always used with
the same constant arguments