LoongArch: KVM: Fix kvm_device leak in kvm_eiointc_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_eiointc_destroy() is not currently doing this, that
would lead to a memory leak.

So, fix it.

Cc: stable@vger.kernel.org
Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Qiang Ma <maqianga@uniontech.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>