devices: Refactor IOAPIC to cover other architectures

IOAPIC, a X86 specific interrupt controller, is referenced by device
manager and CPU manager. To work with more architectures, a common
type for all architectures is needed.
This commit introduces trait InterruptController to provide architecture
agnostic functions. Device manager and CPU manager can use it without
caring what the underlying device is.

Signed-off-by: Michael Zhao <michael.zhao@arm.com>

devices/src/lib.rs

@@ -31,6 +31,7 @@ use std::io;
 #[cfg(feature = "acpi")]
 mod acpi;
 mod bus;
+pub mod interrupt_controller;
 pub mod ioapic;
 pub mod legacy;