Fix a few declarations for the no_std build.

lib/codegen/src/lib.rs

@@ -49,7 +49,6 @@ extern crate failure_derive;
 #[cfg_attr(test, macro_use)]
 extern crate target_lexicon;
 
-#[cfg(feature = "std")]
 #[macro_use]
 extern crate log;
 

lib/codegen/src/regalloc/coalescing.rs

@@ -6,7 +6,6 @@
 //! parameter will belong to the same virtual register as the EBB parameter value itself.
 
 use cursor::{Cursor, EncCursor};
-#[cfg(feature = "std")]
 use dbg::DisplayList;
 use dominator_tree::{DominatorTree, DominatorTreePreorder};
 use flowgraph::{BasicBlock, ControlFlowGraph};