Fix __kuser_cmpxchg inline asm

Author: Amanieu

src/arm_linux.rs

@@ -6,7 +6,7 @@ use core::mem;
 unsafe fn __kuser_cmpxchg(oldval: u32, newval: u32, ptr: *mut u32) -> bool {
     let out: u32;
     // FIXME: we can't use BLX on ARMv4
-    asm!("blx ${0}"
+    asm!("blx ${1}"
          : "={r0}" (out)
          : "r" (0xffff0fc0u32)
            "{r0}" (oldval),