binman: Remove use of Set()

A new built-in set() is used in both Python 2 and 3 now. Move it to use
that instead of Set().

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/bsection.py b/tools/binman/bsection.py
index 0ba542e..be67ff9 100644
--- a/tools/binman/bsection.py
+++ b/tools/binman/bsection.py
@@ -8,7 +8,6 @@
 from __future__ import print_function
 
 from collections import OrderedDict
-from sets import Set
 import sys
 
 import fdt_util
@@ -109,7 +108,7 @@
 
     def GetFdtSet(self):
         """Get the set of device tree files used by this image"""
-        fdt_set = Set()
+        fdt_set = set()
         for entry in self._entries.values():
             fdt_set.update(entry.GetFdtSet())
         return fdt_set
diff --git a/tools/binman/entry.py b/tools/binman/entry.py
index 648cfd2..d842d89 100644
--- a/tools/binman/entry.py
+++ b/tools/binman/entry.py
@@ -18,7 +18,6 @@
     have_importlib = False
 
 import os
-from sets import Set
 import sys
 
 import fdt_util
@@ -178,8 +177,8 @@
         # It would be better to use isinstance(self, Entry_blob_dtb) here but
         # we cannot access Entry_blob_dtb
         if fname and fname.endswith('.dtb'):
-            return Set([fname])
-        return Set()
+            return set([fname])
+        return set()
 
     def ExpandEntries(self):
         pass
diff --git a/tools/binman/state.py b/tools/binman/state.py
index d945e4b..af96786 100644
--- a/tools/binman/state.py
+++ b/tools/binman/state.py
@@ -7,7 +7,6 @@
 
 import hashlib
 import re
-from sets import Set
 
 import os
 import tools
@@ -24,10 +23,10 @@
 use_fake_dtb = False
 
 # Set of all device tree files references by images
-fdt_set = Set()
+fdt_set = set()
 
 # Same as above, but excluding the main one
-fdt_subset = Set()
+fdt_subset = set()
 
 # The DTB which contains the full image information
 main_dtb = None
@@ -136,7 +135,7 @@
     main_dtb = dtb
     fdt_files.clear()
     fdt_files['u-boot.dtb'] = dtb
-    fdt_subset = Set()
+    fdt_subset = set()
     if not use_fake_dtb:
         for image in images.values():
             fdt_subset.update(image.GetFdtSet())