fix: target only gfx906 for HIP compilation

gfx940/gfx1010/gfx1030/gfx1100 cause C++ narrowing errors in ollama's
mma.cuh with hipcc. Since we only have MI50 (gfx906) cards, compile
for gfx906 only. Reduces build time and avoids upstream code bugs.

ai/ollama/Dockerfile

@@ -51,7 +51,7 @@ RUN mkdir -p build-cpu && cd build-cpu && \
 # Step 2: Build HIP backend with hipcc (legacy mode skips enable_language(HIP))
 RUN mkdir -p build-hip && cd build-hip && \
     CC=hipcc CXX=hipcc cmake .. \
-      -DAMDGPU_TARGETS="gfx906:xnack-;gfx940;gfx1010;gfx1030;gfx1100" \
+      -DAMDGPU_TARGETS="gfx906:xnack-" \
       -DCMAKE_BUILD_TYPE=Release && \
     CC=hipcc CXX=hipcc cmake --build . --target ggml-hip -- -l $(nproc) && \
     cmake --install . --component HIP --strip --prefix /build/dist