vmbase: Move Trng internals to arch::aarch64

This commit moves trng implementation from common rand module to a
aarch64 arch module. This is at the moment purely cosmetic change,
however the purpose is move all aarch64 specific code away from common
modules to enable bringup of x86_64 support.

Bug: 362733888
Test: m pvmfw
Test: pVM boots with pvmfw
Change-Id: I5ac315ed38491de8b66f07a5df703cb50786c8bb
diff --git a/libs/libvmbase/src/arch/aarch64.rs b/libs/libvmbase/src/arch/aarch64.rs
index 05b5566..9c4d256 100644
--- a/libs/libvmbase/src/arch/aarch64.rs
+++ b/libs/libvmbase/src/arch/aarch64.rs
@@ -21,6 +21,7 @@
 pub mod linker;
 pub mod page_table;
 pub mod platform;
+pub mod rand;
 pub mod uart;
 
 /// Reads a value from a system register.