LoongArch: Return earlier in die() if notify_die() returns NOTIFY_STOP

After the call to oops_exit(), it should not panic or execute
the crash kernel if the oops is to be suppressed.

Suggested-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>