watchdog: sp5100_tco.c: quiet sparse noise about using plain integer was NULL pointer

Pointers should not be compared to plain integers.
Quiets the sparse warning:
warning: Using plain integer as NULL pointer
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/sp5100_tco.c

@@ -313,7 +313,7 @@ static unsigned char __devinit sp5100_tco_setupdevice(void)
 	tcobase_phys = val;
 
 	tcobase = ioremap(val, SP5100_WDT_MEM_MAP_SIZE);
-	if (tcobase == 0) {
+	if (!tcobase) {
 		pr_err("failed to get tcobase address\n");
 		goto unreg_mem_region;
 	}