configurator: Re-organize module layout

Code in `fdt.rs` do not contain architecture specific code as of
`aarch64`, it's only used by `aarch64`, move it one level up to allow
reusing on riscv64 platform.

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

Author: RuoqingHe

src/configurator/aarch64/mod.rs

@@ -28,9 +28,8 @@ mod x86_64;
 pub use x86_64::*;
 
 #[cfg(target_arch = "aarch64")]
-mod aarch64;
-#[cfg(target_arch = "aarch64")]
-pub use aarch64::*;
+pub mod fdt;
+
 use std::cmp::max;
 use std::mem::size_of;