QBasicAtomicInt: fix wrong comment about non-atomic API

The public documentation for load() and store() says it's atomic,
and it is:
* using _q_value.store(newValue, std::memory_order_relaxed) in the C++11
implementation
* using a simple assignment otherwise, which is atomic (and relaxed, no
memory barriers) on all the existing C++ ABIs.

Change-Id: I40faa47120163225bd11c3a32514ac97ef8bbbd4
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/thread/qbasicatomic.h

@@ -137,12 +137,11 @@ public:
 
     typename Ops::Type _q_value;
 
-    // Non-atomic API
+    // Everything below is either implemented in ../arch/qatomic_XXX.h or (as fallback) in qgenericatomic.h
+
     T load() const Q_DECL_NOTHROW { return Ops::load(_q_value); }
     void store(T newValue) Q_DECL_NOTHROW { Ops::store(_q_value, newValue); }
 
-    // Atomic API, implemented in qatomic_XXX.h
-
     T loadAcquire() const Q_DECL_NOTHROW { return Ops::loadAcquire(_q_value); }
     void storeRelease(T newValue) Q_DECL_NOTHROW { Ops::storeRelease(_q_value, newValue); }