Static linking afcpu with MKL does nt work anymore fro some examples/unittests.

Description

• Did you build ArrayFire yourself or did you use the official installers: ourself, 3.8 branch
• Which backend is experiencing this issue? CPU
• Do you have a workaround? no
• Can the bug be reproduced reliably on your system? yes
• A clear and concise description of what you expected to happen.
  afcpu to link statically with mkl and have no runtime deps with a mkl .so lib

It seems that all cpu tests and examples will fail to link when building with static MKL due to them depending on libmkl_rt.so, which has the two symbols MKL_Set_Threading_Layer, MKL_Set_Interface_Layer that a number of these executables depend on.

Looking at the PR that supported linking with MKL statically
https://github.com/arrayfire/arrayfire/pull/2877/files
we don't see any tests that had depended on the runtime lib...
It looks like this issue was introduced with
cd78885
which creates a dependency on libmkl_rt.so for all MKL builds;
the issue stems from src/api/c/device.cpp, but the MKL specific code is extraneous for a static build and can be deleted without issue.
So, deleting that extra stuff in device.cpp gets everything working.

Reproducible Code and/or Steps

Just try to build 3.8 with static MKL

System Information

1. ArrayFire version: 3.8 branch
2. Devices installed on the system: X86 CPU and MKL 2021.3

Checklist

• Using the latest available ArrayFire release
• GPU drivers are up to date