ACPI, intel_idle: Cleanup idle= internal variables

Having four variables for the same thing:
  idle_halt, idle_nomwait, force_mwait and boot_option_idle_overrides
is rather confusing and unnecessary complex.

if idle= boot param is passed, only set up one variable:
boot_option_idle_overrides

Introduces following functional changes/fixes:
  - intel_idle driver does not register if any idle=xy
    boot param is passed.
  - processor_idle.c will also not register a cpuidle driver
    and get active if idle=halt is passed.
    Before a cpuidle driver with one (C1, halt) state got registered
    Now the default_idle function will be used which finally uses
    the same idle call to enter sleep state (safe_halt()), but
    without registering a whole cpuidle driver.

That means idle= param will always avoid cpuidle drivers to register
with one exception (same behavior as before):
idle=nomwait
may still register acpi_idle cpuidle driver, but C1 will not use
mwait, but hlt. This can be a workaround for IO based deeper sleep
states where C1 mwait causes problems.

Signed-off-by: Thomas Renninger <trenn@suse.de>
cc: x86@kernel.org
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/processor_core.c

@@ -23,7 +23,7 @@ static int set_no_mwait(const struct dmi_system_id *id)
 {
 	printk(KERN_NOTICE PREFIX "%s detected - "
 		"disabling mwait for CPU C-states\n", id->ident);
-	idle_nomwait = 1;
+	boot_option_idle_override = IDLE_NOMWAIT;
 	return 0;
 }
 
@@ -283,7 +283,7 @@ acpi_processor_eval_pdc(acpi_handle handle, struct acpi_object_list *pdc_in)
 {
 	acpi_status status = AE_OK;
 
-	if (idle_nomwait) {
+	if (boot_option_idle_override == IDLE_NOMWAIT) {
 		/*
 		 * If mwait is disabled for CPU C-states, the C2C3_FFH access
 		 * mode will be disabled in the parameter of _PDC object.