[AMD] Split ROCm 7.2 Stage-B large 1-GPU tests into three partitions (#31792)

Co-authored-by: bingxche <bingxche@amd.com>

.github/workflows/pr-test-amd-rocm720.yml

@@ -564,7 +564,7 @@ jobs:
       fail-fast: false
       matrix:
         runner: [linux-mi325-1gpu-sglang]
-        part: [0, 1]
+        part: [0, 1, 2]
     runs-on: ${{matrix.runner}}
     steps:
       - name: Checkout code
@@ -585,7 +585,7 @@ jobs:
       - name: Run test
         timeout-minutes: 45
         run: |
-          bash scripts/ci/amd/amd_ci_exec.sh -w "/sglang-checkout/test" python3 run_suite.py --hw amd --suite stage-b-test-1-gpu-large-amd --auto-partition-id ${{ matrix.part }} --auto-partition-size 2 --timeout-per-file 1800 ${{ needs.check-changes.outputs.continue_on_error == 'true' && '--continue-on-error' || '' }}
+          bash scripts/ci/amd/amd_ci_exec.sh -w "/sglang-checkout/test" python3 run_suite.py --hw amd --suite stage-b-test-1-gpu-large-amd --auto-partition-id ${{ matrix.part }} --auto-partition-size 3 --timeout-per-file 1800 ${{ needs.check-changes.outputs.continue_on_error == 'true' && '--continue-on-error' || '' }}
 
   stage-b-test-2-gpu-large-amd-rocm720:
     needs: [check-changes]