Cleanup vector initialisation - tests

[jjfumero]

Description

Minor refactor

Problem description

n/ a.

Backend/s tested

Mark the backends affected by this PR.

• [X] OpenCL
• [X] PTX
• [X] SPIRV

OS tested

Mark the OS where this PR is tested.

• [X] Linux
• [ ] OSx
• [ ] Windows

Did you check on FPGAs?

If it is applicable, check your changes on FPGAs.

• [ ] Yes
• [X] No

How to test the new patch?

make
make tests