LoongArch: KVM: Fix HW timer interrupt lost when inject interrupt by software

LoongArch: KVM: Fix HW timer interrupt lost when inject interrupt by software

With passthrough HW timer, timer interrupt is injected by HW. When
inject emulated CPU interrupt by software such SIP0/SIP1/IPI, HW timer
interrupt may be lost.

Here check whether there is timer tick value inversion before and after
injecting emulated CPU interrupt by software, timer enabling by reading
timer cfg register is skipped. If the timer tick value is detected with
changing, then timer should be enabled. And inject a timer interrupt by
software if there is.

Cc: <stable@vger.kernel.org>
Fixes: f45ad5b8aa93 ("LoongArch: KVM: Implement vcpu interrupt operations").
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>