mm: Add unit tests for kernel mapping

Add unit tests to evaluate offline correct behavior of memory components:
kernel mappings (address_space.rs).

Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>

src/mm/memory.rs

@@ -101,6 +101,7 @@ pub fn writable_phys_addr(paddr: PhysAddr) -> bool {
 }
 
 #[cfg(test)]
+#[cfg_attr(test_in_svsm, ignore = "Offline testing")]
 mod tests {
     use super::*;
     use crate::address::PhysAddr;