fs: move namespace sysctls and declare fs base directory

This moves the namespace sysctls to its own file as part of the
kernel/sysctl.c spring cleaning

Since we have now removed all sysctls for "fs", we now have to
declare it on the filesystem code, we do that using the new helper,
which reduces boiler plate code.

We rename init_fs_shared_sysctls() to init_fs_sysctls() to reflect
that now fs/sysctls.c is taking on the burden of being the first
to register the base directory as well.

Lastly, since init code will load in the order in which we link it
we have to move the sysctl code to be linked in early, so that its
early init routine runs prior to other fs code. This way, other
filesystem code can register their own sysctls using the helpers
after this:

  * register_sysctl_init()
  * register_sysctl()

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
5 files changed