drm/amdkfd: Fix if preprocessor statement above kfd_fill_iolink_info_for_cpu

Clang warns:

drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_crat.c:866:5: warning:
'CONFIG_X86_64' is not defined, evaluates to 0 [-Wundef]
    ^
1 warning generated.

Fixes: d1c234e2 ("drm/amdkfd: Allow building KFD on ARM64 (v2)")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_crat.c

@@ -863,7 +863,7 @@ static int kfd_fill_mem_info_for_cpu(int numa_node_id, int *avail_size,
 	return 0;
 }
 
-#if CONFIG_X86_64
+#ifdef CONFIG_X86_64
 static int kfd_fill_iolink_info_for_cpu(int numa_node_id, int *avail_size,
 				uint32_t *num_entries,
 				struct crat_subtype_iolink *sub_type_hdr)