csky: abiv1: Fixup compile error

  LD      vmlinux.o
arch/csky/lib/string.o: In function `memmove':
string.c:(.text+0x108): multiple definition of `memmove'
lib/string.o:string.c:(.text+0x7e8): first defined here
arch/csky/lib/string.o: In function `memset':
string.c:(.text+0x148): multiple definition of `memset'
lib/string.o:string.c:(.text+0x2ac): first defined here
scripts/Makefile.vmlinux_o:68: recipe for target 'vmlinux.o' failed
make[4]: *** [vmlinux.o] Error 1

Fixes: e4df2d5e ("csky: Add C based string functions")
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: <stable@vger.kernel.org>

arch/csky/abiv1/inc/abi/string.h

@@ -6,4 +6,10 @@
 #define __HAVE_ARCH_MEMCPY
 extern void *memcpy(void *, const void *, __kernel_size_t);
 
+#define __HAVE_ARCH_MEMMOVE
+extern void *memmove(void *, const void *, __kernel_size_t);
+
+#define __HAVE_ARCH_MEMSET
+extern void *memset(void *, int,  __kernel_size_t);
+
 #endif /* __ABI_CSKY_STRING_H */