sw64: fix ex_table entries from misalignment handlers

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56YD5



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

Add missing local label of stb for handlers of sth, and remove
useless ex_table entries for bis.

Signed-off-by: He Sheng <hesheng@wxiat.com>

Signed-off-by: Gu Zitao <guzitao@wxiat.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>