sw64: add support for restartable sequences

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I73KIX



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Call the rseq_handle_notify_resume() function on return to userspace if
TIF_NOTIFY_RESUME thread flag is set.

Perform fixup on the pre-signal when a signal is delivered on top of a
restartable sequence critical section.

Check that system calls are not invoked from within rseq critical
sections by invoking rseq_syscall() from ret_to_user().
With CONFIG_DEBUG_RSEQ, such behavior results in termination of the
process with SIGSEGV.

Signed-off-by: Mao Minkai <maominkai@wxiat.com>
Reviewed-by: He Sheng <hesheng@wxiat.com>
Signed-off-by: Gu Zitao <guzitao@wxiat.com>