[clang] Fix -Wuninitialized for values passed by const pointers (#147221)

This enables producing a "variable is uninitialized" warning when a
value is passed to a pointer-to-const argument:

```
void foo(const int *);
void test() {
  int *v;
  foo(v);
}
```

Fixes #37460

Author: igorkudrin

clang/lib/Analysis/UninitializedValues.cpp

@@ -446,8 +446,6 @@ void ClassifyRefs::VisitCallExpr(CallExpr *CE) {
       const auto *UO = dyn_cast<UnaryOperator>(Ex);
       if (UO && UO->getOpcode() == UO_AddrOf)
         classify(UO->getSubExpr(), isTrivialBody ? Ignore : ConstPtrUse);
-      else
-        classify(Ex, Ignore);
     }
   }
 }

clang/test/SemaCXX/uninitialized.cpp

@@ -185,6 +185,10 @@ void test_const_ptr() {
   const int *ptr2;
   foo(ptr); // expected-warning {{variable 'ptr' is uninitialized when used here}}
   foobar(&ptr2);
+  int *ptr3; // expected-note {{initialize the variable 'ptr3' to silence this warning}}
+  const int *ptr4; // expected-note {{initialize the variable 'ptr4' to silence this warning}}
+  bar(ptr3); // expected-warning {{variable 'ptr3' is uninitialized when used here}}
+  bar(ptr4); // expected-warning {{variable 'ptr4' is uninitialized when used here}}
 }
 }