Replace no-op with unimplemented!()

src/asm.rs

@@ -8,7 +8,7 @@ macro_rules! instruction {
                 #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
                 () => asm!($asm :::: "volatile"),
                 #[cfg(not(any(target_arch = "riscv32", target_arch = "riscv64")))]
-                () => {}
+                () => unimplemented!(),
             }
         }
     )

src/interrupt.rs

@@ -11,7 +11,7 @@ pub unsafe fn disable() {
         #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
         () => mstatus::clear_mie(),
         #[cfg(not(any(target_arch = "riscv32", target_arch = "riscv64")))]
-        () => {}
+        () => unimplemented!(),
     }
 }
 
@@ -26,7 +26,7 @@ pub unsafe fn enable() {
         #[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
         () => mstatus::set_mie(),
         #[cfg(not(any(target_arch = "riscv32", target_arch = "riscv64")))]
-        () => {}
+        () => unimplemented!(),
     }
 }