further clarify a clCreateBuffer with SVM pointer error condition (#1189

)

It should also be invalid to use SVM host_ptr smaller than `size` in the CL_MEM_COPY_HOST_PTR case

api/opencl_runtime_layer.asciidoc

@@ -628,8 +628,9 @@ returned in _errcode_ret_:
  in the <<memory-flags-table,Memory Flags>> table.
  * {CL_INVALID_BUFFER_SIZE} if _size_ is 0, or if _size_ is greater than
  {CL_DEVICE_MAX_MEM_ALLOC_SIZE} for all devices in _context_, or if
- {CL_MEM_USE_HOST_PTR} is set in _flags_ and _host_ptr_ is a pointer returned by
- {clSVMAlloc} and _size_ is greater than the size passed to {clSVMAlloc}.
+ {CL_MEM_USE_HOST_PTR} or {CL_MEM_COPY_HOST_PTR} is set in _flags_ and
+ _host_ptr_ is a pointer returned by {clSVMAlloc} and _size_ is greater than
+ the size passed to {clSVMAlloc}.
  * {CL_INVALID_HOST_PTR} if _host_ptr_ is `NULL` and {CL_MEM_USE_HOST_PTR} or
  {CL_MEM_COPY_HOST_PTR} are set in _flags_ or if _host_ptr_ is not `NULL`
  but {CL_MEM_COPY_HOST_PTR} or {CL_MEM_USE_HOST_PTR} are not set in _flags_.