scripts: Replace basestring -> str for python3

Python 3 doesn't have basestring type as all string
are unicode strings.

(From OE-Core rev: e8cfab060f4ff3c4c16387871354d407910e87aa)

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

scripts/lib/recipetool/create.py

@@ -167,7 +167,7 @@ class RecipeHandler(object):
         unmappedpc = []
         pcdeps = list(set(pcdeps))
         for pcdep in pcdeps:
-            if isinstance(pcdep, basestring):
+            if isinstance(pcdep, str):
                 recipe = recipemap.get(pcdep, None)
                 if recipe:
                     deps.append(recipe)