KVM: x86: Take advantage of kvm_arch_dy_has_pending_interrupt()

`kvm_arch_dy_runnable` checks the pending_interrupt as the code in
`kvm_arch_dy_has_pending_interrupt`. So take advantage of it.

Signed-off-by: Haiwei Li <lihaiwei@tencent.com>
Message-Id: <20210421032513.1921-1-lihaiwei.kernel@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>