[pvmfw] Move memory flush functions to vmbase

To facilitate reusing the memory management code in rialto later.

Bug: 284462758
Test: m pvmfw_img
Change-Id: I9a544c783ff322d4894f0b3d7e10c0643908d48f
diff --git a/pvmfw/src/dice.rs b/pvmfw/src/dice.rs
index 0aa1273..3116456 100644
--- a/pvmfw/src/dice.rs
+++ b/pvmfw/src/dice.rs
@@ -15,10 +15,10 @@
 //! Support for DICE derivation and BCC generation.
 
 use crate::cstr;
-use crate::helpers::flushed_zeroize;
 use core::ffi::c_void;
 use core::mem::size_of;
 use core::slice;
+use vmbase::memory::flushed_zeroize;
 
 use diced_open_dice::{
     bcc_format_config_descriptor, bcc_handover_main_flow, hash, Config, DiceMode, Hash,