[ROCm][Perf] Allow MTP lens > 1 in Sparse MLA (#36681)

Signed-off-by: Teemu Virolainen <teemu.virolainen@amd.com>

vllm/v1/spec_decode/eagle.py

@@ -214,11 +214,15 @@ class SpecDecodeBaseProposer:
         # Determine allowed attention backends once during initialization.
         self.allowed_attn_types: tuple | None = None
         if current_platform.is_rocm():
+            from vllm.v1.attention.backends.mla.rocm_aiter_mla_sparse import (
+                ROCMAiterMLASparseMetadata,
+            )
             from vllm.v1.attention.backends.rocm_attn import RocmAttentionMetadata
 
             rocm_types = [
                 TritonAttentionMetadata,
                 RocmAttentionMetadata,
+                ROCMAiterMLASparseMetadata,
             ]
             # ROCM_AITER_FA is an optional backend
             # We check is_enabled() here to avoid importing the backend module during