loongarch/kvm: Fix oneshot timer emulation

LoongArch inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8I3QU



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

When oneshot timer is fired, CSR TVAL will be -1 rather than 0.
It is not remaining timer ticks for expired time. There needs
special handing for this situation.

With this patch, runltp with version ltp20230516 passes to run
in vm.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>