arm64: extable: add new extable type "__mc_ex_table"

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5GB28


CVE: NA

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

A new type of extable is added, which is specially used fixup for machine
check safe.
In order to keep kabi consistency, we cannot add type and data members to
struct exception_table_entry(d6e2cc56 arm64: extable: add `type` and
`data` fields), so we put the fixup entry to new extable separately.

Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>