thread: move thread bits accessors to separated file

maillist inclusion
category: feature
bugzilla: 46790
CVE: NA

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



--------------------------------

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>

 Conflicts:
	include/linux/sched.h
[wangxiongfeng: small context conflicts because of inclusion of header
file]
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>