scripts/minikconf.py: s/Error/KconfigParserError

Error is not defined in this script, raise KconfigParserError instead.

Fixes: 82f5181777 ("kconfig: introduce kconfig files")
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Link: https://lore.kernel.org/r/20250820-scripts-minikconf-fixes-v1-2-252041a9125e@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/minikconf.py

@@ -363,7 +363,9 @@ class KconfigParser:
 
     def do_assignment(self, var, val):
         if not var.startswith("CONFIG_"):
-            raise Error('assigned variable should start with CONFIG_')
+            raise KconfigParserError(
+                self, "assigned variable should start with CONFIG_"
+            )
         var = self.data.do_var(var[7:])
         self.data.do_assignment(var, val)