model : re-enable -sm tensor for qwen4exp (#28569)

#27941 disabled -sm tensor for qwen4exp because test-llama-archs asserted on the
Meta device once the fixture carried a PLE layer:
GGML_ASSERT(ggml_backend_buffer_is_meta(tensor->buffer)) at ggml-backend-meta.cpp:476.

With host-resident embeddings the PLE gather is a CPU node and hc_init (the REPEAT
that fans the embedding out to the hc streams) was first reached through layer 0's
PLE path, after that gather. ggml_backend_sched_split_graph pass 2 expands a device
assignment upwards only until it meets a CPU node, so the REPEAT stayed on the CPU
and the later reshape of hc_init inside the meta split viewed a host-resident node.

Expanding hc_init right after it is built puts the REPEAT directly before the first
device node, where pass 2 assigns it; the embedding reshape stays in the CPU split
and is copied in as a split input, as in deepseek4.