ci: Run clippy for each specific feature

The build is run against "--all-features", "pci,acpi", "pci" and "mmio"
separately. The clippy validation must be run against the same set of
features in order to validate the code is correct.

Because of these new checks, this commit includes multiple fixes
related to the errors generated when manually running the checks.

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

vmm/src/cpu.rs

@@ -12,6 +12,7 @@ use crate::device_manager::DeviceManager;
 #[cfg(feature = "acpi")]
 use acpi_tables::{aml, aml::Aml, sdt::SDT};
 use arc_swap::ArcSwap;
+#[cfg(feature = "acpi")]
 use arch::layout;
 use devices::{ioapic, BusDevice};
 use kvm_bindings::CpuId;
@@ -197,6 +198,7 @@ impl CpuidPatch {
     }
 }
 
+#[cfg(feature = "acpi")]
 #[repr(packed)]
 struct LocalAPIC {
     pub r#type: u8,
@@ -747,10 +749,12 @@ impl CpuManager {
     }
 }
 
+#[cfg(feature = "acpi")]
 struct CPU {
     cpu_id: u8,
 }
 
+#[cfg(feature = "acpi")]
 const MADT_CPU_ENABLE_FLAG: usize = 0;
 
 #[cfg(feature = "acpi")]
@@ -813,6 +817,7 @@ impl Aml for CPU {
     }
 }
 
+#[cfg(feature = "acpi")]
 struct CPUNotify {
     cpu_id: u8,
 }
@@ -829,6 +834,7 @@ impl Aml for CPUNotify {
     }
 }
 
+#[cfg(feature = "acpi")]
 struct CPUMethods {
     max_vcpus: u8,
 }