compiler: Tweaks to enable decoupling on GPUs

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 66.66667% with 7 lines in your changes missing coverage. Please review.

Project coverage is 86.69%. Comparing base (ac582e7) to head (9c40360).

Files	Patch %	Lines
devito/arch/archinfo.py	16.66%	5 Missing :warning:
conftest.py	33.33%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2385 +/- ## ========================================== - Coverage 86.82% 86.69% -0.14% ========================================== Files 234 234 Lines 43986 44004 +18 Branches 8126 8127 +1 ========================================== - Hits 38192 38148 -44 - Misses 5087 5154 +67 + Partials 707 702 -5 ```

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