### What this PR does / why we need it?
Add Add constraints for sequence parallelism for unsupported scenarios:
1. tp_size > 1
2. enable_expert_parallel must be True for MoE model
### Does this PR introduce _any_ user-facing change?
### How was this patch tested?
- vLLM version: v0.11.0
- vLLM main:
83f478bb19
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Signed-off-by: realliujiaxu <realliujiaxu@163.com>