sched/cpuset: Only offer CONFIG_CPUSETS if SMP is enabled

Make CONFIG_CPUSETS=y depend on SMP as this feature makes no sense
on UP. This allows for configuring out cpuset_cpumask_can_shrink()
and task_can_attach() entirely, which shrinks the kernel a bit.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170614171926.8345-2-nicolas.pitre@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/init/Kconfig b/init/Kconfig
index 1d3475f..c359038 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1156,6 +1156,7 @@
 
 config CPUSETS
 	bool "Cpuset controller"
+	depends on SMP
 	help
 	  This option will let you create and manage CPUSETs which
 	  allow dynamically partitioning a system into sets of CPUs and