Register indices were only set for the first instance of the array
when the uniform block array was present in both the fragment and
vertex shaders, so this code takes care of the array case.

Change-Id: I8a98470fedcc67bdc5edfd3b852470f5f911d610
Reviewed-on: https://swiftshader-review.googlesource.com/4630Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>