smp/cpumask: Make CONFIG_CPUMASK_OFFSTACK=y usable without debug dependency

When CONFIG_CPUMASK_OFFSTACK was added in 2008, it was dependent upon
CONFIG_DEBUG_PER_CPU_MAPS being enabled, or an architecture could
select it.

The debug dependency adds additional overhead that isn't required
for operation of the feature and which is undesirable for distro
kernels. CONFIG_CPUMASK_OFFSTACK=y is needed to increase the
CONFIG_NR_CPUS value beyond 512 on x86.

So drop the current dependency, its only real dependency is CONFIG_SMP=y.
Signed-off-by: NJosh Boyer <jwboyer@fedoraproject.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20131111140815.GB20328@hansolo.jdub.homelinux.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

lib/Kconfig

@@ -342,7 +342,8 @@ config CHECK_SIGNATURE
 	bool
 
 config CPUMASK_OFFSTACK
-	bool "Force CPU masks off stack" if DEBUG_PER_CPU_MAPS
+	bool "Force CPU masks off stack"
+	depends on SMP
 	help
 	  Use dynamic allocation for cpumask_var_t, instead of putting
 	  them on the stack.  This is a bit more expensive, but avoids