csky: Fix versioncheck warnings

$make versioncheck

arch/csky/include/asm/io.h: 8 linux/version.h not needed.
arch/csky/kernel/process.c: 5 linux/version.h not needed.
arch/csky/mm/dma-mapping.c: 12 linux/version.h not needed.

comments from Randy:

The patch makes sense but these are not compile warnings.
They come from scripts/checkversion.pl, which can be called
by 'make versioncheck', so I suppose that something in your
build system is running 'make versioncheck'.

Signed-off-by: Deyan Wang <wonder_rock@126.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

arch/csky/include/asm/io.h

@@ -5,7 +5,6 @@
 
 #include <linux/pgtable.h>
 #include <linux/types.h>
-#include <linux/version.h>
 
 /*
  * I/O memory access primitives. Reads are ordered relative to any

arch/csky/kernel/process.c

@@ -2,7 +2,6 @@
 // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
 
 #include <linux/module.h>
-#include <linux/version.h>
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
 #include <linux/sched/debug.h>

arch/csky/mm/dma-mapping.c

@@ -9,7 +9,6 @@
 #include <linux/mm.h>
 #include <linux/scatterlist.h>
 #include <linux/types.h>
-#include <linux/version.h>
 #include <asm/cache.h>
 
 static inline void cache_op(phys_addr_t paddr, size_t size,