LoongArch: Fix EENTRY/MERRENTRY setting in setup_tlb_handler()

setup_tlb_handler() is expected to set per-cpu exception handlers, but
it only set the TLBRENTRY successfully because of copy & paste errors,
so fix it.

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