arch, devices, vmm: Remove "acpi" feature gate

Compile this feature in by default as it's well supported on both
aarch64 and x86_64 and we only officially support using it (no non-acpi
binaries are available.)

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

devices/src/acpi.rs

@@ -102,7 +102,6 @@ impl BusDevice for AcpiGedDevice {
     }
 }
 
-#[cfg(feature = "acpi")]
 impl Aml for AcpiGedDevice {
     fn append_aml_bytes(&self, bytes: &mut Vec<u8>) {
         aml::Device::new(

devices/src/lib.rs

@@ -12,7 +12,6 @@ extern crate bitflags;
 #[macro_use]
 extern crate log;
 
-#[cfg(feature = "acpi")]
 pub mod acpi;
 #[cfg(target_arch = "aarch64")]
 pub mod gic;
@@ -21,7 +20,6 @@ pub mod interrupt_controller;
 pub mod ioapic;
 pub mod legacy;
 
-#[cfg(feature = "acpi")]
 pub use self::acpi::{AcpiGedDevice, AcpiPmTimerDevice, AcpiShutdownDevice};
 
 bitflags! {