mainline inclusion
from mainline-v6.2-rc1
commit 19e5eb15
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6BWFP
CVE: NA

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

Introduce the "alternative" mechanism from ARM64 and x86 for LoongArch
to apply runtime patching. The main purpose of this patch is to provide
a framework. In future we can use this mechanism (i.e., the ALTERNATIVE
and ALTERNATIVE_2 macros) to optimize hotspot functions according to cpu
features.
Signed-off-by: NJun Yi <yijun@loongson.cn>
Signed-off-by: NHuacai Chen <chenhuacai@loongson.cn>
Change-Id: I204372e8f1ce7cf3c7bc7de9e8f6f16dbf06239a
(cherry picked from commit caac8f6f)