rust/pv_*: Add more deny lints to pv and pv_core

Denies compiling if one of the following lints find something in pv or
pv_core:
    missing_docs,
    missing_debug_implementations,
    trivial_numeric_casts,
    unstable_features,
    unused_import_braces,
    unused_qualifications

Those lint force developers to avoid unnecessary code and providing
debuggability & documentation for each public symbol.

Fix the compile time error introduced with those lints.

Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

rust/pv/src/brcb.rs

@@ -46,6 +46,7 @@ impl TryFrom<Vec<u8>> for BootHdrTags {
 }
 
 /// Magic value for a SE-(boot)header
+#[derive(Debug)]
 pub struct BootHdrMagic;
 impl MagicValue<8> for BootHdrMagic {
     const MAGIC: [u8; 8] = [0x49, 0x42, 0x4d, 0x53, 0x65, 0x63, 0x45, 0x78];