remove kernel_setsockopt and kernel_getsockopt

[Christoph Hellwig]

Hi Dave,

this series removes the kernel_setsockopt and kernel_getsockopt
functions, and instead switches their users to small functions that
implement setting (or in one case getting) 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 - counter to that a few kernel
drivers just set the fields directly already.

Nevertheless the diffstat looks quite promising:

 42 files changed, 721 insertions(+), 799 deletions(-)