net: mv643xx_eth: fix build failure

The build of sparc allmodconfig fails with the error:
"of_irq_to_resource" [drivers/net/ethernet/marvell/mv643xx_eth.ko]
	undefined!

of_irq_to_resource() is defined when CONFIG_OF_IRQ is defined. And also
CONFIG_OF_IRQ can only be defined if CONFIG_IRQ is defined. So we can
safely use #if defined(CONFIG_OF_IRQ) in the code.
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/mv643xx_eth.c

@@ -2713,7 +2713,7 @@ static const struct of_device_id mv643xx_eth_shared_ids[] = {
 MODULE_DEVICE_TABLE(of, mv643xx_eth_shared_ids);
 #endif
 
-#if defined(CONFIG_OF) && !defined(CONFIG_MV64X60)
+#if defined(CONFIG_OF_IRQ) && !defined(CONFIG_MV64X60)
 #define mv643xx_eth_property(_np, _name, _v)				\
 	do {								\
 		u32 tmp;						\