combo-layer: dont use bb.utils.rename

Bitbake may not be configured, and bb isn't imported anyway.

Instead just use os.rename(), and take the filename from the file object
instead of duplicating logic.

(From OE-Core rev: 528f4fb3683d048537604e4562ea758968060d62)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/combo-layer

@@ -507,7 +507,7 @@ def check_patch(patchfile):
     f.close()
     if of:
         of.close()
-        bb.utils.rename(patchfile + '.tmp', patchfile)
+        os.rename(of.name, patchfile)
 
 def drop_to_shell(workdir=None):
     if not sys.stdin.isatty():