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>

arch/Cargo.toml

@@ -6,6 +6,7 @@ version = "0.1.0"
 
 [features]
 default = []
+fw_cfg = []
 kvm = ["hypervisor/kvm"]
 sev_snp = []
 tdx = []