kunit: cleanup assertion macro internal variables

All the operands should be tagged `const`.
We're only assigning them to variables so that we can compare them (e.g.
check if left == right, etc.) and avoid evaluating expressions multiple
times.

There's no need for them to be mutable.

Also rename the helper variable `loc` to `__loc` like we do with
`__assertion` and `__strs` to avoid potential name collisions with user
code.

Signed-off-by: Daniel Latypov <[e-mail]>
Reviewed-by: David Gow <[e-mail]>
Reviewed-by: Brendan Higgins <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

include/kunit/test.h

···
 
 #define KUNIT_ASSERTION(test, assert_type, pass, assert_class, INITIALIZER, fmt, ...) do { \
 	if (unlikely(!(pass))) {					       \
-		static const struct kunit_loc loc = KUNIT_CURRENT_LOC;	       \
+		static const struct kunit_loc __loc = KUNIT_CURRENT_LOC;       \
 		struct assert_class __assertion = INITIALIZER;		       \
 		kunit_do_failed_assertion(test,				       \
-					  &loc,				       \
+					  &__loc,			       \
 					  assert_type,			       \
 					  &__assertion.assert,		       \
 					  fmt,				       \
···
 				    fmt,				       \
 				    ...)				       \
 do {									       \
-	typeof(left) __left = (left);					       \
-	typeof(right) __right = (right);				       \
+	const typeof(left) __left = (left);				       \
+	const typeof(right) __right = (right);				       \
 	static const struct kunit_binary_assert_text __text = {		       \
 		.operation = #op,					       \
 		.left_text = #left,					       \
···
 						fmt,			       \
 						...)			       \
 do {									       \
-	typeof(ptr) __ptr = (ptr);					       \
+	const typeof(ptr) __ptr = (ptr);				       \
 									       \
 	KUNIT_ASSERTION(test,						       \
 			assert_type,					       \