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/Cargo.toml

@@ -5,7 +5,7 @@ authors = ["The Chromium OS Authors"]
 edition = "2018"
 
 [dependencies]
-acpi_tables = { path = "../acpi_tables", optional = true }
+acpi_tables = { path = "../acpi_tables" }
 anyhow = "1.0.56"
 arch = { path = "../arch" }
 bitflags = "1.3.2"
@@ -22,6 +22,5 @@ vmm-sys-util = "0.9.0"
 
 [features]
 default = []
-acpi = ["acpi_tables"]
 cmos = []
 fwdebug = []