Tighten error description for clSetKernelArgDevicePointerEXT

Current wording of error conditions for clSetKernelArgDevicePointerEXT says:
“should be noted that it’s legal to pass invalid pointers as the value (similarly to C/C++ function calls with pointer arguments) as long as the kernel doesn’t dereference the pointer.”

We think this could be misinterpreted to mean that invalid pointers are only permissible when the kernel does not dereference them.

Propose that it be rewritten as:
“It should be noted that it is legal to pass invalid pointers as the value (similarly to C/C++ function calls with pointer arguments).”

Would also like to add this additional clarification:
“Passing invalid pointers to clSetKernelArgDevicePointerEXT may result in undefined behavior depending on how they are used within the kernel.”

Search the OpenCL-Docs sources for the clSetKernelArgDevicePointerEXT entry and read its current error-condition wording. Replace the ambiguous sentence with the proposed clarification and add the undefined-behavior note, then verify that the rendered documentation preserves both statements.

Written by the indexing model from the issue text.