powerpc: Fix compiler warning for the relocatable kernel

Fixes this warning:
 arch/powerpc/kernel/setup_64.c:447:5: warning: "kernstart_addr" is not defined

which arises because PHYSICAL_START is no longer a constant when
CONFIG_RELOCATABLE=y.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/setup_64.c

@@ -444,9 +444,9 @@ void __init setup_system(void)
 	if (htab_address)
 		printk("htab_address                  = 0x%p\n", htab_address);
 	printk("htab_hash_mask                = 0x%lx\n", htab_hash_mask);
-#if PHYSICAL_START > 0
-	printk("physical_start                = 0x%lx\n", PHYSICAL_START);
-#endif
+	if (PHYSICAL_START > 0)
+		printk("physical_start                = 0x%lx\n",
+		       PHYSICAL_START);
 	printk("-----------------------------------------------------\n");
 
 	DBG(" <- setup_system()\n");