[POWERPC] ppc: Include <asm/cacheflush.h> in kernel/ppc_ksyms.c

It needs it:

	arch/ppc/kernel/ppc_ksyms.c:152: error: '__flush_icache_range'
	undeclared here (not in a function)

and a few more like that.
Signed-off-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/ppc/kernel/ppc_ksyms.c

@@ -24,6 +24,7 @@
 #include <asm/checksum.h>
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
+#include <asm/cacheflush.h>
 #include <linux/adb.h>
 #include <linux/cuda.h>
 #include <linux/pmu.h>