Correct cufft_utils scaling_kernel indexing

[icyveins7]

The scaling_kernel was clearly designed to be a grid-stride kernel to multiply all elements by a constant; this correction makes it so.

While the examples currently build and run correctly as-is, if the parameters are changed (like in 1d_r2c_c2r) to be a larger value, it becomes highly likely that the output will be wrong, as only a few elements will be 'scaled' multiple times.

[kvoronin]

Hi @icyveins7

We have changed the license of the repository from BSD-3 to Apache 2.0 to allow accepting external contributions in the right way.

What this means is that

• the new default branch is main. (The old one called master is still there, but master and an extra bsd3_main are not supposed to be changed)
• all commits to the repository must be signed, see the new https://github.com/NVIDIA/CUDALibrarySamples/blob/main/CONTRIBUTING.md. Technically, it is as simple as doing git commit -s ... which would enforce DCO for the contribution (see more details in the CONTRIBUTING.md).

What this means for this PR:
Please change the target branch to main (potentially instead of rebase it is easier to cherry-pick commits into a new branch) and sign the commits.

Thanks!