ac/registers: use better names for disambiguated definitions

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
diff --git a/src/amd/registers/makeregheader.py b/src/amd/registers/makeregheader.py
index 859a59b..1d73cb4 100644
--- a/src/amd/registers/makeregheader.py
+++ b/src/amd/registers/makeregheader.py
@@ -44,10 +44,10 @@
 # Chips are sorted chronologically
 CHIPS = [
     Object(name='gfx6', disambiguation='GFX6'),
-    Object(name='gfx7', disambiguation='GFX6'),
-    Object(name='gfx8', disambiguation='GFX6'),
-    Object(name='fiji', disambiguation='GFX6'),
-    Object(name='stoney', disambiguation='GFX6'),
+    Object(name='gfx7', disambiguation='GFX7'),
+    Object(name='gfx8', disambiguation='GFX8'),
+    Object(name='fiji', disambiguation='GFX8'),
+    Object(name='stoney', disambiguation='GFX8'),
     Object(name='gfx9', disambiguation='GFX9'),
 ]