aarch64: Remove unnecessary function definitions

This is a refactoring commit to simplify source code.
Removed some functions that only return a layout const.

Signed-off-by: Michael Zhao <michael.zhao@arm.com>

arch/src/lib.rs

@@ -85,8 +85,8 @@ pub mod aarch64;
 #[cfg(target_arch = "aarch64")]
 pub use aarch64::{
     arch_memory_regions, configure_system, configure_vcpu, fdt::DeviceInfoForFdt,
-    get_host_cpu_phys_bits, get_kernel_start, get_uefi_start, initramfs_load_addr, layout,
-    layout::CMDLINE_MAX_SIZE, layout::IRQ_BASE, uefi, EntryPoint,
+    get_host_cpu_phys_bits, initramfs_load_addr, layout, layout::CMDLINE_MAX_SIZE,
+    layout::IRQ_BASE, uefi, EntryPoint,
 };
 
 #[cfg(target_arch = "x86_64")]