PCI: bus speed strings should be const

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index 659eaa0..968cfea 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -49,7 +49,7 @@
 }
 
 /* these strings match up with the values in pci_bus_speed */
-static char *pci_bus_speed_strings[] = {
+static const char *pci_bus_speed_strings[] = {
 	"33 MHz PCI",		/* 0x00 */
 	"66 MHz PCI",		/* 0x01 */
 	"66 MHz PCI-X", 	/* 0x02 */