more asm cleanup

src/compiler/arch/riscv/mod.rs

@@ -1,11 +1,9 @@
 mod asm;
 mod compile;
 mod reg;
-mod single;
 mod instr;
 
 use crate::util::BitsI32;
-use single::*;
 
 pub use asm::*;
 pub use compile::*;