LoongArch: KVM: Remove timer interrupt injection when SW timer expired

LoongArch: KVM: Remove timer interrupt injection when SW timer expired

The software timer emulation is to wake up vCPU when the vCPU executes
idle instruction and gives up host CPU, the vCPU timer tick value and
interrupt is set when vCPU is scheduled in.

It is not necessary to inject timer interrupt when SW timer is expired.
Here remove it, also use common API kvm_vcpu_wake_up() to wake up vCPU.

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