Remove the use of a template qUnused function for ICC

ICC 12 does not seem to need this.

Change-Id: I98e9d530e767c4d24424f0c2b5d763f863e85fe4
Reviewed-by: Stephen Kelly <stephen.kelly@kdab.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
(backported from qt5/qtbase d3951a5b0f4fe9731d1512668b43f51bd98bd84e)
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@theqtcompany.com>