QTimer: Avoid implicit conversion warnings

This fixes compiling an application using QTimer and -Wshorten-64-to-32
on a 64-bit system without getting this warning:

 ... 5.8/clang_64/lib/QtCore.framework/Headers/qtimer.h:171:21:
 warning: implicit conversion loses integer precision: 'rep'
 (aka 'long long') to 'int' [-Wshorten-64-to-32]
         setInterval(value.count());
         ~~~~~~~~~~~ ^~~~~~~~~~~~~

Change-Id: I3e0407a7193c841308f7271c41a8dd5a2eb2a534
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/kernel/qtimer.h

@@ -168,7 +168,7 @@ public:
     Q_ALWAYS_INLINE
     void setInterval(std::chrono::milliseconds value)
     {
-        setInterval(value.count());
+        setInterval(int(value.count()));
     }
 
     Q_ALWAYS_INLINE