sw64: fix sys_rt_sigaction

Sunway inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I56XYC



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

__ARCH_HAS_SA_RESTORER was defined to fix compile error in the past.
However, this changed the offset of sa_mask in struct sigaction and
made sys_rt_sigaction unable to get sa_mask passed from user.

To fix this problem, the old sigaction and the related structs are
added back, macro define __ARCH_HAS_SA_RESTORER is removed.

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