[pvmfw] Move assembly wrappers to vmbase for reuse

In both pvmfw and rialo.

Test: atest libpvmfw.bootargs.test
Test: m pvmfw_img
Bug: 282928116

Change-Id: If93cfca26cddcc27aca15baae85a0f7609160c42
diff --git a/pvmfw/src/exceptions.rs b/pvmfw/src/exceptions.rs
index e819729..4b24d14 100644
--- a/pvmfw/src/exceptions.rs
+++ b/pvmfw/src/exceptions.rs
@@ -14,11 +14,12 @@
 
 //! Exception handlers.
 
+use crate::helpers::page_4kb_of;
 use crate::memory::{MemoryTrackerError, MEMORY};
-use crate::{helpers::page_4kb_of, read_sysreg};
 use core::fmt;
 use vmbase::console;
 use vmbase::logger;
+use vmbase::read_sysreg;
 use vmbase::{eprintln, power::reboot};
 
 const UART_PAGE: usize = page_4kb_of(console::BASE_ADDRESS);