powerpc/mpc5xxx: delete unneeded test before of_node_put

Of_node_put supports NULL as its argument, so the initial test is not
necessary.

Suggested by Uwe Kleine-König.

The semantic patch that fixes this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e;
@@

-if (e)
   of_node_put(e);
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/sysdev/mpc5xxx_clocks.c

@@ -26,7 +26,6 @@ unsigned long mpc5xxx_get_bus_frequency(struct device_node *node)
 		of_node_put(node);
 		node = np;
 	}
-	if (node)
 	of_node_put(node);
 
 	return p_bus_freq ? *p_bus_freq : 0;