Work around ifx automatic-offloading bugs

[rouson]

This PR works around issues that arise when the following build command is used to tell the ifx compiler to automatically offload do concurrent constructs to a GPU:

fpm test --compiler ifx --flag "-coarray -coarray-num-images=1 -fopenmp-target-do-concurrent -qopenmp -fopenmp-targets=spir64"

The workarounds are

1. further reduce iterations in trainable_engine_test_m so training converges with ifx without crashing
2. convert do concurrent with array statements to do loops