RISC-V: Fix duplicate included thread_info.h

asm/thread_info.h is included more than once, Remove the one that isn't
necessary.

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

Author: Tian Tao

arch/riscv/kernel/head.S

@@ -3,7 +3,6 @@
  * Copyright (C) 2012 Regents of the University of California
  */
 
-#include <asm/thread_info.h>
 #include <asm/asm-offsets.h>
 #include <asm/asm.h>
 #include <linux/init.h>