Function calls in kernels not called

```julia
using KernelAbstractions

@kernel function kernel(v)
I = @index(Global, Linear)
@show I # loops over 1:10

end

function inlined_function(v, I)
@show I
end

@kernel function nested_kernel(v)
I = @index(Global, Linear)
@show I # I only loop over 1:1

inlined_function(v, I)
end

v = ones(10)
wait(kernel(CPU())(v, ndrange = 10))
wait(nested_kernel(CPU())(v, ndrange = 10))
```
Edit: Updated with working code.

Start by running the Julia reproducer from the issue with KernelAbstractions and compare the output from kernel and nested_kernel. Trace how the nested kernel function call is handled, and consider the issue resolved when the function executes for each of the 10 indices rather than only once.

Written by the indexing model from the issue text.