Make CPURead/WriteFunc structure 'const'

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

hw/syborg_timer.c

@@ -162,13 +162,13 @@ static void syborg_timer_write(void *opaque, target_phys_addr_t offset,
     }
 }
 
-static CPUReadMemoryFunc *syborg_timer_readfn[] = {
+static CPUReadMemoryFunc * const syborg_timer_readfn[] = {
     syborg_timer_read,
     syborg_timer_read,
     syborg_timer_read
 };
 
-static CPUWriteMemoryFunc *syborg_timer_writefn[] = {
+static CPUWriteMemoryFunc * const syborg_timer_writefn[] = {
     syborg_timer_write,
     syborg_timer_write,
     syborg_timer_write