OCL: fixed C4505

fix for http://build.opencv.org/builders/win_x86%5Bdebug%5D--%5Bsse_%3D_ON%5D--%5Btbb_%3D_ON%5D--%5Bgpu_%3D_ON%5D--%5Bcompiler_%3D_vc10%5D--%5Btests_%3D_ON%5D-/builds/493/steps/compile%20debug%2032%20vc10%20shared%20n/logs/build%20summary%20%28e%3A%200%2C%20w%3A%202%29 introduced by https://github.com/Itseez/opencv/pull/2527