Missing indexing on `GPUSparseDeviceMatrixCSC`

The lack of specialized `getindex` methods for `GPUSparseDeviceMatrixCSC` makes it so that we cannot index into it (the previous `CuSparseDeviceMatrixCSC` could). As a consequence, we also cannot index into `GPUSparseDeviceColumnView`. I understand that it is not the most efficient as we need to perform a binary search, but in my use case, it is the only option.

## MWE in terms of `GPUSparseDeviceColumnView`
```julia
using CUDA, SparseArrays

A = sprand(10, 10, 0.4)
A_gpu = cu(A)
a_gpu = @view A_gpu[:, 1]

function kernel(out, a)
acc = 0.0
i = 1
while i <= length(a)
acc += a[i]
i += 1
end

out[1] = acc
return nothing
end

out = CUDA.zeros(1)

@cuda kernel(out, a_gpu)
```

The kernel can equivalently be written as the following ([subarray.jl:313](https://github.com/JuliaLang/julia/blob/01a2eadb0474c395845e66ed3382b52e0c1f1b8f/base/subarray.jl#L313)).
```julia
function kernel(out, a)
acc = 0.0
i = 1
while i <= length(a)
index = Base.reindex(a.indices, (i,))
v = a.parent[index...]
acc += v
i += 1
end

out[1] = acc
return nothing
end
```
In this case, it succeeds with reindexing, i.e. to find the index within the parent (`A_gpu`), but since `GPUSparseDeviceMatrixCSC` lacks appropriate indexing methods, it fails with the error message (under julia with option -g2).
```
index: (1, 1)
ERROR: a exception was thrown during kernel execution on thread (1, 1, 1) in block (1, 1, 1).
Stacktrace:
[1] error_if_canonical_getindex at ./abstractarray.jl:1357
[2] getindex at ./abstractarray.jl:1341
[3] kernel at ./REPL[7]:6
```