Rust: fix clear_cache ARM ASM

Author: angelsl

lib/builtins/clear_cache.c

@@ -104,7 +104,7 @@ void __clear_cache(void *start, void *end) {
          const register int flags __asm("r2") = 0;
          const register int syscall_nr __asm("r7") = __ARM_NR_cacheflush;
         __asm __volatile("svc 0x0" : "=r"(start_reg)
-            : "r"(syscall_nr), "r"(start_reg), "r"(end_reg), "r"(flags) : "r0");
+            : "r"(syscall_nr), "r"(start_reg), "r"(end_reg), "r"(flags));
          if (start_reg != 0) {
              compilerrt_abort();
          }