Derive common traits for write enums like for read enums

The enums are just values so this should do no harm, and it helps
building interfaces around the peripherals that do validation or
otherwise pass those values around.

Closes: #135

Author: chrysn

src/generate/register.rs

@@ -685,6 +685,7 @@ pub fn fields(
                     let variants_doc = variants.iter().map(|v| &*v.doc);
                     mod_items.push(quote! {
                         #[doc = #pc_w_doc]
+                        #[derive(Clone, Copy, Debug, PartialEq)]
                         pub enum #pc_w {
                             #(#[doc = #variants_doc]
                             #variants_pc),*