vmm: Add acpi table for fw_cfg device

This allows the fw_cfg device to be recognized by the guest linux
kernel. This becomes more relavnt in the following cl where I add
the option to load files into the guest via fw_cfg. The Linux kernel
already has a fw_cfg driver that will automatically load these files
under /sys when CONFIG_FW_CFG_SYSFS is enabled in the kernel config

For arm we must add fw_cfg to the devices tree

Signed-off-by: Alex Orozco <alexorozco@google.com>

devices/Cargo.toml

@@ -44,6 +44,6 @@ arch = { path = "../arch" }
 
 [features]
 default = []
-fw_cfg = ["bitfield-struct", "linux-loader", "zerocopy"]
+fw_cfg = ["arch/fw_cfg", "bitfield-struct", "linux-loader", "zerocopy"]
 kvm = ["arch/kvm"]
 pvmemcontrol = []