hexagon: add support for CONCAT op (#23648)

* hexagon: add support for CONCAT with optimized concat_2d_transposed

qwen3.5 models are quite heavy on the CONCAT with large and transposed src1.

* hex-concat: use fastdiv in generic version

* hex-concat: make checks for transposed a bit more readable

* hex-concat: reoder dma ops for better pipelining

* hex-cont/cpy: optimize CPY and CONT ops

The primary change is to avoid scalar divs in the inner loops.
We were calling hvx_copy_uu(... type_size) where type_size is non a constexpr.
This causes runtime divs by that value which is normally just 4 or 2 (f32/f16).

* hex-get-rows: optimize GET_ROWS for large rows

We now use DMA for larger rows and also split them into chunks to improve perf for Qwen3.5 and other models
that do lots of GET_ROWS with huge (2MB+ rows).

Also bump the DMA queue depth now that we can take advantage of it.

* hex-concat: unroll the inner loops of concat_2d

* hex-concat: more updates to concat_2d to improve perf a bit further

* hex-cpy: fixed n_rows per thread checks in the copy ops

* hmx-fa: fix alignment issues while computing dma sizes

* hex-set-rows: add early returns for idle threads

* hvx-rope: minor optimization to replace loops with fastdiv logic

* hex-rope: replace scalar tail processing with HVX

* hex-rope: optimize rope cache init with HVX

Add hvx-utils sin/cos helpers that use an aprox method (similar to rsqrt, inverse, etc)
Use the helpers to optimize ROPE.

ggml/src/ggml-hexagon/htp/main.c

@@ -420,8 +420,7 @@ AEEResult htp_iface_start(remote_handle64 handle, uint32 sess_id, uint64 dsp_que
 
     ctx->n_threads = n_hvx;
     for (int i = 0; i < ctx->n_threads; i++) {
-        // see discussion https://github.com/ggml-org/llama.cpp/pull/18151#discussion_r2632388541
-        ctx->dma[i] = dma_queue_create(128);
+        ctx->dma[i] = dma_queue_create(256); // queue depth
     }
 
     // init worker pool
@@ -601,6 +600,9 @@ static int execute_op(struct htp_ops_context * octx) {
         case HTP_OP_PAD:
             return op_pad(octx);
 
+        case HTP_OP_CONCAT:
+            return op_concat(octx);
+
         case HTP_OP_GATED_DELTA_NET:
             return op_gated_delta_net(octx);