powerpc: Remove get_irq_desc()

get_irq_desc() is a powerpc-specific version of irq_to_desc(). That
is reason enough to remove it, but it also doesn't know about sparse
irq_desc support which irq_to_desc() does (when we enable it).

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/crash.c b/arch/powerpc/kernel/crash.c
index 0a8439a..6f4613d 100644
--- a/arch/powerpc/kernel/crash.c
+++ b/arch/powerpc/kernel/crash.c
@@ -373,7 +373,7 @@
 	hard_irq_disable();
 
 	for_each_irq(i) {
-		struct irq_desc *desc = irq_desc + i;
+		struct irq_desc *desc = irq_to_desc(i);
 
 		if (desc->status & IRQ_INPROGRESS)
 			desc->chip->eoi(i);