x86: 0 -> NULL, for arch/x86_64

When comparing a pointer, it's clearer to compare it to NULL than to 0.

[ tglx: arch/x86 adaptation ]
Signed-off-by: Yoann Padioleau <padator@wanadoo.fr>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: ak@suse.de
Cc: discuss@x86-64.org
Cc: akpm@linux-foundation.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/mm/numa_64.c

@@ -166,7 +166,7 @@ early_node_mem(int nodeid, unsigned long start, unsigned long end,
 		return __va(mem);
 	ptr = __alloc_bootmem_nopanic(size,
 				SMP_CACHE_BYTES, __pa(MAX_DMA_ADDRESS));
-	if (ptr == 0) {
+	if (ptr == NULL) {
 		printk(KERN_ERR "Cannot find %lu bytes in node %d\n",
 			size, nodeid);
 		return NULL;