scripts: Make mkdtboimg.py compatible with python3

There are a few changes needed to run mkdtboimg.py with python3.
-No more implicit conversion between char and byte.
-xrange was renamed to range in python3
-floor division must be done with the  '//' operator

Bug: 166496956
Test: ./mkdtboimg_testdata.sh
Test: atest FirmwareDtboVerification
Change-Id: I8b9b97b7b9f31768cc133f37d0144420cb1a0e81
Signed-off-by: Forenche <prahul2003@gmail.com>
Signed-off-by: Richard Raya <rdxzv.dev@gmail.com>

scripts/dtc/libfdt/mkdtboimg.py

@@ -244,7 +244,7 @@ class Dtbo(object):
         Tree table entries and update the DTBO header.
         """
 
-        self.__metadata = array('c', ' ' * self.__metadata_size)
+        self.__metadata = array('b', b' ' * self.__metadata_size)
         metadata_offset = self.header_size
         for dt_entry in self.__dt_entries:
             self._update_dt_entry_header(dt_entry, metadata_offset)
@@ -290,7 +290,7 @@ class Dtbo(object):
         if self.__dt_entries:
             raise ValueError('DTBO DT entries can be added only once')
 
-        offset = self.dt_entries_offset / 4
+        offset = self.dt_entries_offset // 4
         params = {}
         params['dt_file'] = None
         for i in range(0, self.dt_entry_count):
@@ -465,7 +465,7 @@ class Dtbo(object):
         dt_offset = (self.header_size +
                      dt_entry_count * self.dt_entry_size)
 
-        dt_entry_buf = ""
+        dt_entry_buf = b""
         for dt_entry in dt_entries:
             if not isinstance(dt_entry, DtEntry):
                 raise ValueError('Adding invalid DT entry object to DTBO')
@@ -612,7 +612,7 @@ def parse_dt_entries(global_args, arg_list):
         raise ValueError('Input DT images must be provided')
 
     total_images = len(img_file_idx)
-    for idx in xrange(total_images):
+    for idx in range(total_images):
         start_idx = img_file_idx[idx]
         if idx == total_images - 1:
             argv = arg_list[start_idx:]
@@ -769,7 +769,7 @@ def parse_dump_cmd_args(arglist):
 
     parser = argparse.ArgumentParser(prog='dump')
     parser.add_argument('--output', '-o', nargs='?',
-                        type=argparse.FileType('wb'),
+                        type=argparse.FileType('w'),
                         dest='outfile',
                         default=stdout)
     parser.add_argument('--dtb', '-b', nargs='?', type=str,
@@ -789,7 +789,7 @@ def parse_config_create_cmd_args(arglist):
     """
     parser = argparse.ArgumentParser(prog='cfg_create')
     parser.add_argument('conf_file', nargs='?',
-                        type=argparse.FileType('rb'),
+                        type=argparse.FileType('r'),
                         default=None)
     cwd = os.getcwd()
     parser.add_argument('--dtb-dir', '-d', nargs='?', type=str,