scripts: python3: use explicit relative imports

Implicit relative imports within packages are not supported in
python 3. They have to be converted to explicit imports.

Used 'from .module import' syntax for relative imports.

(From meta-yocto rev: 8eb2befc544e29fd87ac1fc75886cc6d7f40ad90)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/bsp/engine.py

@@ -34,7 +34,7 @@
 import os
 import sys
 from abc import ABCMeta, abstractmethod
-from tags import *
+from .tags import *
 import shlex
 import json
 import subprocess

scripts/lib/bsp/kernel.py

@@ -32,8 +32,7 @@ import shutil
 from tags import *
 import glob
 import subprocess
-from engine import create_context
-
+from .engine import create_context
 
 def find_bblayers():
     """