powerpc: Remove all usages of NO_IRQ

NO_IRQ has been == 0 on powerpc for just over ten years (since commit
0ebfff1491ef ("[POWERPC] Add new interrupt mapping core and change
platforms to use it")). It's also 0 on most other arches.

Although it's fairly harmless, every now and then it causes confusion
when a driver is built on powerpc and another arch which doesn't define
NO_IRQ. There's at least 6 definitions of NO_IRQ in drivers/, at least
some of which are to work around that problem.

So we'd like to remove it. This is fairly trivial in the arch code, we
just convert:

    if (irq == NO_IRQ)	to	if (!irq)
    if (irq != NO_IRQ)	to	if (irq)
    irq = NO_IRQ;	to	irq = 0;
    return NO_IRQ;	to	return 0;

And a few other odd cases as well.

At least for now we keep the #define NO_IRQ, because there is driver
code that uses NO_IRQ and the fixes to remove those will go via other
trees.

Note we also change some occurrences in PPC sound drivers, drivers/ps3,
and drivers/macintosh.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/sysdev/cpm1.c b/arch/powerpc/sysdev/cpm1.c
index 81d4947..3c0eb9b 100644
--- a/arch/powerpc/sysdev/cpm1.c
+++ b/arch/powerpc/sysdev/cpm1.c
@@ -132,7 +132,7 @@
 {
 	struct device_node *np = NULL;
 	struct resource res;
-	unsigned int sirq = NO_IRQ, hwirq, eirq;
+	unsigned int sirq = 0, hwirq, eirq;
 	int ret;
 
 	pr_debug("cpm_pic_init\n");
@@ -154,7 +154,7 @@
 		goto end;
 
 	sirq = irq_of_parse_and_map(np, 0);
-	if (sirq == NO_IRQ)
+	if (!sirq)
 		goto end;
 
 	/* Initialize the CPM interrupt controller. */
@@ -168,7 +168,7 @@
 	cpm_pic_host = irq_domain_add_linear(np, 64, &cpm_pic_host_ops, NULL);
 	if (cpm_pic_host == NULL) {
 		printk(KERN_ERR "CPM2 PIC: failed to allocate irq host!\n");
-		sirq = NO_IRQ;
+		sirq = 0;
 		goto end;
 	}
 
@@ -182,7 +182,7 @@
 	}
 
 	eirq = irq_of_parse_and_map(np, 0);
-	if (eirq == NO_IRQ)
+	if (!eirq)
 		goto end;
 
 	if (setup_irq(eirq, &cpm_error_irqaction))