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>

arch/powerpc/sysdev/mv64x60_pic.c

@@ -213,7 +213,7 @@ static int mv64x60_host_map(struct irq_host *h, unsigned int virq,
 {
 	int level1;
 
-	get_irq_desc(virq)->status |= IRQ_LEVEL;
+	irq_to_desc(virq)->status |= IRQ_LEVEL;
 
 	level1 = (hwirq & MV64x60_LEVEL1_MASK) >> MV64x60_LEVEL1_OFFSET;
 	BUG_ON(level1 > MV64x60_LEVEL1_GPP);