of: fdt: remove unnecessary codes

While unflattening the device tree, we try to populate dt nodes and
properties into tree-shaped data structure.

In populate_properties function, pprev is initially set to
&np->properties, and then updated to &pp->next.

In both scenarios *pprev is NULL, since the memory area that we are
allocating from is initially zeroed.

I tested the code as below, and it showed that BUG was never called.

-       if (!dryrun)
+       if (!dryrun) {
+               if (*pprev)
+                       BUG();
                *pprev = NULL;
+       }

Let's remove unnecessary code.
Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com>
Link: https://lore.kernel.org/r/20210701140457epcms1p2cc43a7c62150f012619feab913f017af@epcms1p2Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/fdt.c

@@ -200,9 +200,6 @@ static void populate_properties(const void *blob,
 				 nodename, (char *)pp->value);
 		}
 	}
-
-	if (!dryrun)
-		*pprev = NULL;
 }
 
 static int populate_node(const void *blob,