pvmfw: Remove unnecessary flush of the guest DT

There is not need to flush it manually now that MemoryTracker flushes
R/W memory when dropped.

Note: This flush() had no effect due to a bug in Fdt::header() causing
      fdt.as_slice() == &[].

Test: atest MicrodroidHostTests
Change-Id: I56678bd0535217a0c246f480c94685378ac7ec59
diff --git a/pvmfw/src/entry.rs b/pvmfw/src/entry.rs
index 965d6b9..bbfc2ea 100644
--- a/pvmfw/src/entry.rs
+++ b/pvmfw/src/entry.rs
@@ -248,7 +248,6 @@
     )?;
 
     helpers::flushed_zeroize(bcc_slice);
-    helpers::flush(slices.fdt.as_slice());
 
     info!("Expecting a bug making MMIO_GUARD_UNMAP return NOT_SUPPORTED on success");
     MEMORY.lock().as_mut().unwrap().mmio_unmap_all().map_err(|e| {