[SYCL] Add BF16 support to GET_ROWS operation (#21391)

Add GGML_TYPE_BF16 to the SYCL backend's GET_ROWS operation, both in
supports_op and in the kernel dispatch. This fixes a performance
regression where models using BF16 embedding tensors (e.g., Gemma4's
per_layer_token_embd.weight) fall back to CPU for the GET_ROWS op,
causing a full GPU-to-CPU tensor transfer every token.

The fix reuses the existing get_rows_sycl_float template with
sycl::ext::oneapi::bfloat16, matching the pattern already used for
sycl::half (F16) and float (F32).

Author: devedse

ggml/src/ggml-sycl/getrows.cpp

@@ -183,6 +183,10 @@ void ggml_sycl_op_get_rows(ggml_backend_sycl_context & ctx, ggml_tensor * dst) {
             get_rows_sycl_float(ctx, dst->src[0], dst->src[1], dst, (const sycl::half *)dst->src[0]->data,
                                 src1_i32, (float *)dst->data, ctx.stream());
             break;
+        case GGML_TYPE_BF16:
+            get_rows_sycl_float(ctx, dst->src[0], dst->src[1], dst, (const sycl::ext::oneapi::bfloat16 *)dst->src[0]->data,
+                                src1_i32, (float *)dst->data, ctx.stream());
+            break;
         case GGML_TYPE_F32:
             get_rows_sycl_float(ctx, dst->src[0], dst->src[1], dst, (const float *)dst->src[0]->data,
             src1_i32, (float *)dst->data, ctx.stream());

ggml/src/ggml-sycl/ggml-sycl.cpp

@@ -4974,6 +4974,7 @@ static bool ggml_backend_sycl_device_supports_op(ggml_backend_dev_t dev, const g
             {
                 switch (op->src[0]->type) {
                     case GGML_TYPE_F16:
+                    case GGML_TYPE_BF16:
                     case GGML_TYPE_F32:
                     case GGML_TYPE_Q4_0:
                     case GGML_TYPE_Q4_1: