pci: Simplify PciDevice trait

There's no need for assign_irq() or assign_msix() functions from the
PciDevice trait, as we can see it's never used anywhere in the codebase.
That's why it's better to remove these methods from the trait, and
slightly adapt the existing code.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

pci/src/device.rs

@@ -4,11 +4,9 @@
 
 use crate::configuration::{self, PciBarRegionType};
 use crate::msix::MsixTableEntry;
-use crate::PciInterruptPin;
 use devices::BusDevice;
 use std::any::Any;
 use std::fmt::{self, Display};
-use std::sync::Arc;
 use std::{self, io, result};
 use vm_allocator::SystemAllocator;
 use vm_memory::{GuestAddress, GuestUsize};
@@ -56,19 +54,6 @@ pub struct BarReprogrammingParams {
 }
 
 pub trait PciDevice: BusDevice {
-    /// Assign a legacy PCI IRQ to this device.
-    /// The device may write to `irq_evt` to trigger an interrupt.
-    fn assign_pin_irq(
-        &mut self,
-        _irq_cb: Arc<InterruptDelivery>,
-        _irq_num: u32,
-        _irq_pin: PciInterruptPin,
-    ) {
-    }
-
-    /// Assign MSI-X to this device.
-    fn assign_msix(&mut self) {}
-
     /// Allocates the needed PCI BARs space using the `allocate` function which takes a size and
     /// returns an address. Returns a Vec of (GuestAddress, GuestUsize) tuples.
     fn allocate_bars(