thread: move thread bits accessors to separated file

maillist inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8JVJ3
CVE: NA

Reference: https://github.com/norov/linux/commits/ilp32-5.2



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Thread bits may be accessed from low-level code, so isolating is a measure
to avoid circular dependencies in header files.

The exact reason for circular dependency is WARN_ON() macro added in patch
edd63a27 "set_restore_sigmask() is never called without SIGPENDING (and
never should be)"

Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
Signed-off-by: Yury Norov <ynorov@marvell.com>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>