intel_idle: Graceful probe failure when MWAIT is disabled

When MWAIT is disabled, intel_idle refuses to probe.
But it may mis-lead the user by blaming this on the model number:

intel_idle: does not run on family 6 modesl 79

So defer the check for MWAIT until after the model# white-list check succeeds,
and if the MWAIT check fails, tell the user how to fix it:

intel_idle: Please enable MWAIT in BIOS SETUP
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/idle/intel_idle.c

@@ -1066,7 +1066,7 @@ static const struct idle_cpu idle_cpu_dnv = {
 };
 
 #define ICPU(model, cpu) \
-	{ X86_VENDOR_INTEL, 6, model, X86_FEATURE_MWAIT, (unsigned long)&cpu }
+	{ X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY, (unsigned long)&cpu }
 
 static const struct x86_cpu_id intel_idle_ids[] __initconst = {
 	ICPU(INTEL_FAM6_NEHALEM_EP,		idle_cpu_nehalem),
@@ -1130,6 +1130,11 @@ static int __init intel_idle_probe(void)
 		return -ENODEV;
 	}
 
+	if (!boot_cpu_has(X86_FEATURE_MWAIT)) {
+		pr_debug("Please enable MWAIT in BIOS SETUP\n");
+		return -ENODEV;
+	}
+
 	if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
 		return -ENODEV;