hexagon: add HTP kernel for GGML_OP_GATED_DELTA_NET (#22837)

Implement the Gated Delta Net recurrence on HVX with:
- 4-row fused kernels for PP (prompt processing) path
- 8-row fused kernels for TG (token generation) path, reducing
  K/Q/gate vector reload overhead by 2x
- Separate PP/TG thread functions for I-cache isolation
- VTCM state scratchpad with DMA in/out for TG single-cycle access
- Vectorized gate exp via hvx_exp_f32

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

@@ -594,6 +594,9 @@ static int execute_op(struct htp_ops_context * octx) {
         case HTP_OP_SOLVE_TRI:
             return op_solve_tri(octx);
 
+        case HTP_OP_GATED_DELTA_NET:
+            return op_gated_delta_net(octx);
+
         case HTP_OP_INVALID:
             break;