wan: make read-only data const

Change several wan drivers to make strings and other initialize
only parameters const.

Compile tested only (with no new warnings)

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/wan/pc300_drv.c b/drivers/net/wan/pc300_drv.c
index c6aa66e..fbf1175 100644
--- a/drivers/net/wan/pc300_drv.c
+++ b/drivers/net/wan/pc300_drv.c
@@ -1,5 +1,5 @@
 #define	USE_PCI_CLOCK
-static char rcsid[] = 
+static const char rcsid[] =
 "Revision: 3.4.5 Date: 2002/03/07 ";
 
 /*