genirq: Protect tglx from tripping over his own feet

The irq_desc.status field will either go away or renamed to
settings. Anyway we need to maintain compatibility to avoid breaking
the world and some more. While moving bits into the core, I need to
avoid that I use any of the still existing IRQ_ bits in the core code
by typos. So that file will hold the inline wrappers and some nasty
CPP tricks to break the build when typoed.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/irq/internals.h

@@ -13,6 +13,8 @@
 # define IRQ_BITMAP_BITS	NR_IRQS
 #endif
 
+#include "settings.h"
+
 #define istate core_internal_state__do_not_mess_with_it
 
 extern int noirqdebug;

kernel/irq/irqdesc.c

@@ -79,7 +79,7 @@ static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node)
 	desc->irq_data.chip_data = NULL;
 	desc->irq_data.handler_data = NULL;
 	desc->irq_data.msi_desc = NULL;
-	desc->status = IRQ_DEFAULT_INIT_FLAGS;
+	desc->status = _IRQ_DEFAULT_INIT_FLAGS;
 	desc->handle_irq = handle_bad_irq;
 	desc->depth = 1;
 	desc->irq_count = 0;
@@ -246,7 +246,7 @@ int __init early_irq_init(void)
 
 struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
 	[0 ... NR_IRQS-1] = {
-		.status		= IRQ_DEFAULT_INIT_FLAGS,
+		.status		= _IRQ_DEFAULT_INIT_FLAGS,
 		.handle_irq	= handle_bad_irq,
 		.depth		= 1,
 		.lock		= __RAW_SPIN_LOCK_UNLOCKED(irq_desc->lock),

kernel/irq/settings.h

+/*
+ * Internal header to deal with irq_desc->status which will be renamed
+ * to irq_desc->settings.
+ */
+enum {
+	_IRQ_DEFAULT_INIT_FLAGS	= IRQ_DEFAULT_INIT_FLAGS,
+};