mfd: Check for mem_base when building IORESOURCE_MEM resources

If mem_base is NULL, then we fall back to the default case, just copying the
original resource.
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

drivers/mfd/mfd-core.c

@@ -48,7 +48,7 @@ static int mfd_add_device(struct device *parent, int id,
 		res[r].flags = cell->resources[r].flags;
 
 		/* Find out base to use */
-		if (cell->resources[r].flags & IORESOURCE_MEM) {
+		if ((cell->resources[r].flags & IORESOURCE_MEM) && mem_base) {
 			res[r].parent = mem_base;
 			res[r].start = mem_base->start +
 				cell->resources[r].start;