fix(mlir/**.py): fix comparison to None (#94019)

from PEP8
(https://peps.python.org/pep-0008/#programming-recommendations):

> Comparisons to singletons like None should always be done with is or
is not, never the equality operators.

Co-authored-by: Eisuke Kawashima <e-kwsm@users.noreply.github.com>

Author: e-kwsm

mlir/test/python/ir/affine_expr.py

@@ -42,7 +42,7 @@ def testAffineExprEq():
         # CHECK: False
         print(a1 == a3)
         # CHECK: False
-        print(a1 == None)
+        print(a1 is None)
         # CHECK: False
         print(a1 == "foo")
 

mlir/test/python/ir/attributes.py

@@ -56,8 +56,8 @@ def testAttrEq():
         print("a1 == a2:", a1 == a2)
         # CHECK: a1 == a3: True
         print("a1 == a3:", a1 == a3)
-        # CHECK: a1 == None: False
-        print("a1 == None:", a1 == None)
+        # CHECK: a1 is None: False
+        print("a1 is None:", a1 is None)
 
 
 # CHECK-LABEL: TEST: testAttrHash
@@ -109,9 +109,9 @@ def testAttrEqDoesNotRaise():
         # CHECK: False
         print(a1 == not_an_attr)
         # CHECK: False
-        print(a1 == None)
+        print(a1 is None)
         # CHECK: True
-        print(a1 != None)
+        print(a1 is not None)
 
 
 # CHECK-LABEL: TEST: testAttrCapsule

mlir/test/python/ir/builtin_types.py

@@ -57,8 +57,8 @@ def testTypeEq():
     print("t1 == t2:", t1 == t2)
     # CHECK: t1 == t3: True
     print("t1 == t3:", t1 == t3)
-    # CHECK: t1 == None: False
-    print("t1 == None:", t1 == None)
+    # CHECK: t1 is None: False
+    print("t1 is None:", t1 is None)
 
 
 # CHECK-LABEL: TEST: testTypeHash
@@ -143,9 +143,9 @@ def testTypeEqDoesNotRaise():
     # CHECK: False
     print(t1 == not_a_type)
     # CHECK: False
-    print(t1 == None)
+    print(t1 is None)
     # CHECK: True
-    print(t1 != None)
+    print(t1 is not None)
 
 
 # CHECK-LABEL: TEST: testTypeCapsule