arm64: fix USER_DS definition problem in non-compat mode

hulk inclusion
category: bugfix
bugzilla: 51788
CVE: NA

--------

For some platforms which CONFIG_COMPAT is not set, the function 'is_compat_task'
is not declared. Therefore, the macro USER_DS cannot be defined using the function
'is_compat_task' in this case.

Fixes: 2ef73d5148e3 ("arm64: fix current_thread_info()->addr_limit setup")
Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
Reviewed-by: Chang Liao <liaochang1@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>