pvmfw: Use Fdt::as_ptr() during logging

Test: m pvmfw_bin
Change-Id: I8f845ce77c9ad3bb651fcf6713bf50e36681e095
diff --git a/libs/libfdt/src/lib.rs b/libs/libfdt/src/lib.rs
index 29d7abe..927bf50 100644
--- a/libs/libfdt/src/lib.rs
+++ b/libs/libfdt/src/lib.rs
@@ -614,7 +614,8 @@
         fdt_err_expect_zero(ret)
     }
 
-    fn as_ptr(&self) -> *const c_void {
+    /// Return a shared pointer to the device tree.
+    pub fn as_ptr(&self) -> *const c_void {
         self as *const _ as *const c_void
     }