AArch64: don't expose FDT to kernel

There is a check that if FDT is stub when ACPI table initialized in
linux kernel [1]. So, if full FDT is given, FDT will be used instead of
ACPI. It is aginst our primary goal to use UEFI. So, full FDT can't
be given here. For simplicity, just neglict it here. Remember that this
is just a workaround as we are required to pass a FDT to kernel/grub to
meet Arm Base Boot Requirement 7.4.3 [2].

It can be improved by making a stub FDT and pass it through configuration
table. Maybe later.

Fixes: #261
Signed-off-by: Jianyong Wu <[email protected]>

[1] https://github.com/torvalds/linux/blob/d528014517f2b0531862c02865b9d4c908019dc4/arch/arm64/kernel/acpi.c#L203
[2] https://developer.arm.com/documentation/den0044/latest

src/efi/mod.rs

@@ -1115,6 +1115,10 @@ pub fn efi_exec(
     let mut ct_index = 0;
 
     // Populate with FDT table if present
+    // To boot linux kernel with ACPI, we can't offer full fdt. Simply, neglect
+    // it. See
+    // https://github.com/torvalds/linux/blob/d528014517f2b0531862c02865b9d4c908019dc4/arch/arm64/kernel/acpi.c#L203
+    #[cfg(not(target_arch = "aarch64"))]
     if let Some(fdt_entry) = info.fdt_reservation() {
         ct[ct_index] = efi::ConfigurationTable {
             vendor_guid: Guid::from_fields(