Fix CI: use api-docs/include for OpenVX headers

The Khronos sample implementation stores core OpenVX headers (vx.h,
vx_nodes.h, vxu.h) in api-docs/include/VX/, not include/VX/.

Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>

Author: kiritigowda

.github/workflows/ci.yml

@@ -34,7 +34,7 @@ jobs:
       - name: Build openvx-mark
         run: |
           mkdir build && cd build
-          cmake -DOPENVX_INCLUDES=/tmp/openvx-sample/include \
+          cmake -DOPENVX_INCLUDES=/tmp/openvx-sample/api-docs/include \
                 -DOPENVX_LIB_DIR=${{ steps.openvx.outputs.lib_dir }} ..
           cmake --build . -j$(nproc)