Revert "Remove private_no_mangle_static directives in generated code for latest"

This reverts commit 15064a9.

Author: craigjb

src/generate/device.rs

@@ -193,6 +193,7 @@ pub fn render(d: &Device, target: &Target, nightly: bool, device_x: &mut String)
         // version)
         #[allow(renamed_and_removed_lints)]
         // This currently breaks on nightly, to be removed with the line above once 1.31 is stable
+        #[allow(private_no_mangle_statics)]
         #[no_mangle]
         static mut DEVICE_PERIPHERALS: bool = false;
 

src/generate/interrupt.rs

@@ -139,6 +139,7 @@ pub fn render(
 
                 #[allow(renamed_and_removed_lints)]
                 // This currently breaks on nightly, to be removed with the line above once 1.31 is stable
+                #[allow(private_no_mangle_statics)]
                 #[cfg(feature = "rt")]
                 #[doc(hidden)]
                 #[link_section = ".vector_table.interrupts"]