Removed usage of half types in CTS test

[kamil-goras-mobica]

#1982

[bashbaug]

This isn't the correct fix - sorry for poorly explaining what needs to be done!

We want to keep the testing for CL_HALF_FLOAT. In other words, we shouldn't lose any test covereage after making these changes.

We want to remove the dependency on cl_khr_fp16 for these tests though, so the tests that currently require cl_khr_fp16 (which are used to test CL_HALF_FLOAT) need to be modified.

See the discussion here: #1974

One possible solution would be to eliminate all usage pointers to the half4 type by switching to pointers to the half type instead. This should allow removal of cl_khr_fp16, because pointers to the half type used by the vload_half and vstore_half functions is in core OpenCL.

A better (but more involved) solution is to eliminate all usage of half4, vload_half, and vstore_half, period, and switch to float reference data instead.

Let's chat more tomorrow if you have questions - thanks!

[bashbaug]

I'm going to remove the "focused review" label until updates have been made.

[kamil-goras-mobica]

@bashbaug I created corrections in separate PR: #2147