LoongArch: Simplify "BLT foo, zero" with BLTZ

mainline inclusion
from mainline-v5.19
commit d1bc75d7
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5OHOB


CVE: NA

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Support for the syntactic sugar is present in upstream binutils port
from the beginning. Use it for shorter lines and better consistency.
Generated code should be identical.

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