No more calls.S. It becomes simpler to add a new syscall.

1. kernel/include/linux/syscalls.h
   Define the syscall:
   asmlinkage long sys_hong(int k);
2. implement it somewere.c
3. kernel/include/uapi/asm-generic/unistd.h
   Link the syscall with a number. Don’t forget update __NR_syscalls accordingly.
   e.g.,
   #define __NR_hong 291
   __SYSCALL(__NR_hong, sys_hong)
   #define __NR_syscalls 292