constify string pointers to save a little space

No need for these pointers to be writable.

BUG=None
TEST=CQ passes

Change-Id: Ie76e36fb5e639cb77d895e377109bb81da7ad105
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/rootdev/+/5544863
Tested-by: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Commit-Queue: Gwendal Grignou <gwendal@chromium.org>
diff --git a/rootdev.c b/rootdev.c
index a953299..8775e92 100644
--- a/rootdev.c
+++ b/rootdev.c
@@ -33,8 +33,8 @@
  */
 #define MAX_SLAVE_DEPTH 8
 
-static const char *kDefaultSearchPath = "/sys/block";
-static const char *kDefaultDevPath = "/dev";
+static const char kDefaultSearchPath[] = "/sys/block";
+static const char kDefaultDevPath[] = "/dev";
 
 /* Encode the root device structuring here for Chromium OS */
 static const char kActiveRoot[] = "/dev/ACTIVE_ROOT";