vmbase: Move crosvm layout to aarch64

Crosvm provide architecture specific memory layout and set of peripheral devices. This commit move layout definition to aarch64 specific code directories as  a preparation before adding new CPU architecture.

Bug: 362733888
Test: m libvmbase

Change-Id: Ia8e82eb928d5fdc444581ca6fee145d2324a3591
diff --git a/libs/libvmbase/src/arch.rs b/libs/libvmbase/src/arch.rs
index 5cb578b..d6095e5 100644
--- a/libs/libvmbase/src/arch.rs
+++ b/libs/libvmbase/src/arch.rs
@@ -20,6 +20,9 @@
 #[cfg(target_arch = "aarch64")]
 pub use aarch64::platform;
 
+#[cfg(target_arch = "aarch64")]
+pub use aarch64::layout;
+
 /// Write with well-defined compiled behavior.
 ///
 /// See https://github.com/rust-lang/rust/issues/131894
@@ -47,7 +50,6 @@
             let line_size = aarch64::min_dcache_line_size();
             let end = start + size;
             let start = crate::util::unchecked_align_down(start, line_size);
-
             for line in (start..end).step_by(line_size) {
                 crate::dc!("cvau", line);
             }