csky: Optimize abiv2 copy_to_user_page with VM_EXEC

Only when vma is for VM_EXEC, we need sync dcache & icache. eg:
 - gdb ptrace modify user space instruction code area.

Add VM_EXEC condition to reduce unnecessary cache flush.

The abiv1 cpus' cache are all VIPT, so we still need to deal with
dcache aliasing problem. But there is optimized way to use cache
color, just like what's done in arch/csky/abiv1/inc/abi/page.h.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>

arch/csky/abiv2/inc/abi/cacheflush.h

@@ -37,7 +37,9 @@ static inline void flush_dcache_page(struct page *page)
 #define copy_to_user_page(vma, page, vaddr, dst, src, len) \
 do { \
 	memcpy(dst, src, len); \
-	cache_wbinv_range((unsigned long)dst, (unsigned long)dst + len); \
+	if (vma->vm_flags & VM_EXEC) \
+		cache_wbinv_range((unsigned long)dst, \
+				  (unsigned long)dst + len); \
 } while (0)
 #define copy_from_user_page(vma, page, vaddr, dst, src, len) \
 	memcpy(dst, src, len)