libfdt: Fix bug in fdt_subnode_offset_namelen()

There's currently an off-by-one bug in fdt_subnode_offset_namelen()
which causes it to keep searching after it's finished the subnodes of
the given parent, and into the subnodes of siblings of the original
node which come after it in the tree.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

libfdt/fdt_ro.c

@@ -112,12 +112,12 @@ int fdt_num_mem_rsv(const void *fdt)
 int fdt_subnode_offset_namelen(const void *fdt, int offset,
 			       const char *name, int namelen)
 {
-	int depth;
+	int depth = 0;
 
 	FDT_CHECK_HEADER(fdt);
 
-	for (depth = 0;
-	     offset >= 0;
+	for (depth = 0, offset = fdt_next_node(fdt, offset, &depth);
+	     (offset >= 0) && (depth > 0);
 	     offset = fdt_next_node(fdt, offset, &depth)) {
 		if (depth < 0)
 			return -FDT_ERR_NOTFOUND;
@@ -126,7 +126,10 @@ int fdt_subnode_offset_namelen(const void *fdt, int offset,
 			return offset;
 	}
 
-	return offset; /* error */
+	if (offset < 0)
+		return offset; /* error */
+	else
+		return -FDT_ERR_NOTFOUND;
 }
 
 int fdt_subnode_offset(const void *fdt, int parentoffset,