[libclc] Scalar vloada_half should be removed

[StuartDBrady]

The scalar vloada_half should be removed as per KhronosGroup/OpenCL-Docs/issues/648.

It is declared in generic/include/clc/shared/vload.h – see the comment "Scalar vload_half also needs to be declared" which is incorrect as of KhronosGroup/OpenCL-CTS/pull/1293.

It is defined in generic/lib/shared/vload.cl by __FUNC with vloada_half##SUFFIX from through the inclusion of vload_half.inc.

Note that the scalar vload_half is needed and should not be removed.

[llvmbot]

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