libc: Pass the last argument in __luna_syscall5 correctly

libs/libc/src/luna/syscall.c

@@ -42,7 +42,7 @@ long int __luna_syscall5(long int sys_num, unsigned long int arg0, unsigned long
 {
     long int result;
     register unsigned long int value0 asm("r10") = arg3;
-    register unsigned long int value1 asm("r10") = arg4;
+    register unsigned long int value1 asm("r8") = arg4;
     asm volatile("int $0x42" : "=a"(result) : "a"(sys_num), "D"(arg0), "S"(arg1), "d"(arg2), "r"(value0), "r"(value1));
     return result;
 }