Allow more characters in partition name links

We have several partitions with underscores in their names
which would not be properly linked in:
/dev/block/platform/msm_sdcc.1/by-name/

With this change more characters (_-.) are allowed in
partition name links. Also, any other character is
replaced with '_' so the resulting link names have the
same length as the partition name.

Change-Id: I746566c03db98b10326c755692362d2c10e528ae
diff --git a/init/util.c b/init/util.c
index 918bc05..76af9e5 100755
--- a/init/util.c
+++ b/init/util.c
@@ -305,14 +305,27 @@
     return 0;
 }
 
+/*
+ * replaces any unacceptable characters with '_', the
+ * length of the resulting string is equal to the input string
+ */
 void sanitize(char *s)
 {
+    const char* accept =
+            "abcdefghijklmnopqrstuvwxyz"
+            "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+            "0123456789"
+            "_-.";
+
     if (!s)
         return;
-    while (isalnum(*s))
-        s++;
-    *s = 0;
+
+    for (; *s; s++) {
+        s += strspn(s, accept);
+        if (*s) *s = '_';
+    }
 }
+
 void make_link(const char *oldpath, const char *newpath)
 {
     int ret;