Fix get_node_by_path string equality check

When determining if to recurse into a node, get_node_by_path does not
check if the length of each node name is equal.  If searching for
/foo/baz, this can result in recursing into /foobar because
strneq("foo", "foobar", 3) is true.

This can result in a reference to /foo/baz to be incorrectly set to
/foobar/baz.  A test for this was added.

Signed-off-by: Tim Montague <tmontague@ghs.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

tests/path-references.dts

@@ -12,4 +12,17 @@
 		ref = &{/node1}; /* reference after target */
 		lref = &n1;
 	};
+	/* Check references to nested nodes with common prefix */
+	foobar {
+		n3: baz {
+			ref = &{/foo/baz};
+			lref = &n4;
+		};
+	};
+	foo {
+		n4: baz {
+			ref = &{/foobar/baz};
+			lref = &n3;
+		};
+	};
 };