LoongArch: Use ABI names of registers where appropriate

mainline inclusion
from mainline-v5.19
commit d8e7f201
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5OHOB


CVE: NA

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

Some of the assembly in the LoongArch port seem to come from a
prehistoric time, when the assembler didn't even have support for the
ABI names we all come to know and love, thus used raw register numbers
which hampered readability.

The usages are found with a regex match inside arch/loongarch, then
manually adjusted for those non-definitions.

Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>