Mild optimization of qt_hash

Move one AND operation out of the loop, as it is only needed in the end.

Change-Id: I48adcd18c900654830a84813f26c95eee579b49d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit fc947593ef78c92b67811ac14dae200b45b480ea)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/tools/qhash.cpp

@@ -1085,16 +1085,13 @@ void qSetGlobalQHashSeed(int newSeed)
 */
 uint qt_hash(QStringView key, uint chained) noexcept
 {
-    auto n = key.size();
-    auto p = key.utf16();
-
     uint h = chained;
 
-    while (n--) {
+    for (auto c: key) {
-        h = (h << 4) + *p++;
+        h = (h << 4) + c.unicode();
         h ^= (h & 0xf0000000) >> 23;
-        h &= 0x0fffffff;
     }
+    h &= 0x0fffffff;
     return h;
 }