ACPI: Reintroduce run time configurable max_cstate for !CPU_IDLE case

This was writeable in 2.6.23 but the cpuidle merge made it read-only.  But
some people's scripts (ie: Mark's) were writing to it.

As an unhappy compromise, make max_cstate writeable again if the kernel was
configured without CONFIG_CPU_IDLE.

http://bugzilla.kernel.org/show_bug.cgi?id=9683

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Mark Lord <lkml@rtr.ca>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/processor_idle.c

@@ -76,7 +76,11 @@ static void (*pm_idle_save) (void) __read_mostly;
 #define PM_TIMER_TICKS_TO_US(p)		(((p) * 1000)/(PM_TIMER_FREQUENCY/1000))
 
 static unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER;
+#ifdef CONFIG_CPU_IDLE
 module_param(max_cstate, uint, 0000);
+#else
+module_param(max_cstate, uint, 0644);
+#endif
 static unsigned int nocst __read_mostly;
 module_param(nocst, uint, 0000);