LoongArch: Make LTO case independent in Makefile

LTO is not only used for Clang, but maybe also used for Rust, make LTO
case out of CONFIG_CC_HAS_ANNOTATE_TABLEJUMP in Makefile.

This is preparation for later patch, no function changes.

Cc: stable@vger.kernel.org
Suggested-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>