Make CPURead/WriteFunc structure 'const'

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/hw/cs4231.c b/hw/cs4231.c
index f13815b..82e2f52 100644
--- a/hw/cs4231.c
+++ b/hw/cs4231.c
@@ -129,13 +129,13 @@
     }
 }
 
-static CPUReadMemoryFunc *cs_mem_read[3] = {
+static CPUReadMemoryFunc * const cs_mem_read[3] = {
     cs_mem_readl,
     cs_mem_readl,
     cs_mem_readl,
 };
 
-static CPUWriteMemoryFunc *cs_mem_write[3] = {
+static CPUWriteMemoryFunc * const cs_mem_write[3] = {
     cs_mem_writel,
     cs_mem_writel,
     cs_mem_writel,