Address const issues in preparation for libcxx rebase.

Change-Id: If9bf6c3ee57c3476a5661401853506551e2150cb
diff --git a/init/devices.cpp b/init/devices.cpp
index 557a6ac..e74140b 100644
--- a/init/devices.cpp
+++ b/init/devices.cpp
@@ -413,7 +413,7 @@
 static char **get_character_device_symlinks(struct uevent *uevent)
 {
     const char *parent;
-    char *slash;
+    const char *slash;
     char **links;
     int link_num = 0;
     int width;
@@ -467,7 +467,7 @@
 {
     const char *device;
     struct platform_node *pdev;
-    char *slash;
+    const char *slash;
     const char *type;
     char buf[256];
     char link_path[256];