sysctl: Remove dead code from sysctl_check

Now that the sys_sysctl is now a compatibility wrapper around
/proc/sys we can remove much of sysctl_check and reduce it
to a few remaining sanity checks.  This completely decouples
it from the binary sysctl system call.

Little things like ensuring that the sysctl has not already
been registered are all that remain.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

lib/Kconfig.debug

@@ -912,7 +912,7 @@ config LATENCYTOP
 
 config SYSCTL_SYSCALL_CHECK
 	bool "Sysctl checks"
-	depends on SYSCTL_SYSCALL
+	depends on SYSCTL
 	---help---
 	  sys_sysctl uses binary paths that have been found challenging
 	  to properly maintain and use. This enables checks that help