remove unused asm feature flag

src/libboard_artiq/src/lib.rs

@@ -1,7 +1,6 @@
 #![no_std]
 #![feature(never_type)]
 #![feature(naked_functions)]
-#![feature(asm)]
 
 extern crate core_io;
 extern crate crc;

src/libio/lib.rs

@@ -1,6 +1,5 @@
 #![no_std]
 #![feature(never_type)]
-#![feature(asm)]
 
 #[cfg(feature = "alloc")]
 extern crate alloc;

src/libksupport/src/lib.rs

@@ -3,7 +3,6 @@
 #![feature(const_btree_new)]
 #![feature(inline_const)]
 #![feature(naked_functions)]
-#![feature(asm)]
 
 #[macro_use]
 extern crate alloc;