Change strlen to sizeof

Index: grub/util/getroot.c
===================================================================
--- grub.orig/util/getroot.c	2012-01-31 00:36:16.026730000 -0600
+++ grub/util/getroot.c	2012-01-31 00:36:25.296311000 -0600
@@ -799,9 +799,9 @@
     grub_util_error (_("Storage name for `%s' not NUL-terminated"), dir);
 
   os_dev = xmalloc (2 * sizeof (os_dev[0]));
-  os_dev[0] = xmalloc (strlen ("/dev/") + data_len);
-  memcpy (os_dev[0], "/dev/", strlen ("/dev/"));
-  memcpy (os_dev[0] + strlen ("/dev/"), data, data_len);
+  os_dev[0] = xmalloc (sizeof ("/dev/") - 1 + data_len);
+  memcpy (os_dev[0], "/dev/", sizeof ("/dev/") - 1);
+  memcpy (os_dev[0] + sizeof ("/dev/") - 1, data, data_len);
   os_dev[1] = 0;
 
   if (ports && num_ports > 0)