kunit: tool: simplify kconfig is_subset_of() logic

Don't use an O(nm) algorithm* and make it more readable by using a dict.

*Most obviously, it does a nested for-loop over the entire other config.
A bit more subtle, it calls .entries(), which constructs a set from the
list for _every_ outer iteration.

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: dlatypov

tools/testing/kunit/kunit_config.py

@@ -41,15 +41,14 @@ def add_entry(self, entry: KconfigEntry) -> None:
 		self._entries.append(entry)
 
 	def is_subset_of(self, other: 'Kconfig') -> bool:
+		other_dict = {e.name: e.value for e in other.entries()}
 		for a in self.entries():
-			found = False
-			for b in other.entries():
-				if a.name != b.name:
+			b = other_dict.get(a.name)
+			if b is None:
+				if a.value == 'n':
 					continue
-				if a.value != b.value:
-					return False
-				found = True
-			if a.value != 'n' and found == False:
+				return False
+			elif a.value != b:
 				return False
 		return True