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/sysdev/fsl_msi.c b/arch/powerpc/sysdev/fsl_msi.c
index da38a1f..7174374 100644
--- a/arch/powerpc/sysdev/fsl_msi.c
+++ b/arch/powerpc/sysdev/fsl_msi.c
@@ -55,7 +55,7 @@
 {
 	struct irq_chip *chip = &fsl_msi_chip;
 
-	get_irq_desc(virq)->status |= IRQ_TYPE_EDGE_FALLING;
+	irq_to_desc(virq)->status |= IRQ_TYPE_EDGE_FALLING;
 
 	set_irq_chip_and_handler(virq, chip, handle_edge_irq);