LoongArch: KVM: Fix kvm_device leak in kvm_pch_pic_destroy()

In the Linux kernel, the following vulnerability has been resolved: LoongArch: KVM: Fix kvm_device leak in kvm_pch_pic_destroy() In kvm_ioctl_create_device(), kvm_device has allocated memory, kvm_device->destroy() seems to be supposed to free its kvm_device struct, but kvm_pch_pic_destroy() is not currently doing this, that would lead to a memory leak. So, fix it.