Move sysctl check into debugging section and don't make it default y

I noticed that sysctl_check.o was the largest object file in
a allnoconfig build in kernel/*.

  36243       0       0   36243    8d93 kernel/sysctl_check.o

This is because it was default y and && EMBEDDED. But I don't
really see a need for a non kernel developer to have their
sysctls checked all the time.

So move the Kconfig into the kernel debugging section and
also drop the default y and the EMBEDDED check.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>