OCL: Remove mul24

Remove mul24 since `id` can be larger 2^23. If id is not in [-2^23, 2^23-1], the multiplication result is implementation-defined.
For example, 4K 3-channel: 3840 × 2160 × 3 = 24883200 > 2^23.

check_regression=OCL*Norm*:OCL*MeanStdDev*
test_filter=OCL*Norm*:OCL*MeanStdDev*
build_examples=OFF
test_modules=core