patman: Drop tools.ToChar() and ToChars()

This is useful anymore, since we always want to call chr() in Python 3.
Drop it and adjust callers to use chr().

Also drop ToChars() which is no-longer used.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/dtoc/fdt.py b/tools/dtoc/fdt.py
index cb365ca..4a78c73 100644
--- a/tools/dtoc/fdt.py
+++ b/tools/dtoc/fdt.py
@@ -87,9 +87,9 @@
             return Type.STRING, [s.decode() for s in strings[:-1]]
     if size % 4:
         if size == 1:
-            return Type.BYTE, tools.ToChar(data[0])
+            return Type.BYTE, chr(data[0])
         else:
-            return Type.BYTE, [tools.ToChar(ch) for ch in list(data)]
+            return Type.BYTE, [chr(ch) for ch in list(data)]
     val = []
     for i in range(0, size, 4):
         val.append(data[i:i + 4])
@@ -152,9 +152,9 @@
                 if type(self.value) == list:
                     new_value = []
                     for val in self.value:
-                        new_value += [tools.ToChar(by) for by in val]
+                        new_value += [chr(by) for by in val]
                 else:
-                    new_value = [tools.ToChar(by) for by in self.value]
+                    new_value = [chr(by) for by in self.value]
                 self.value = new_value
             self.type = newprop.type