arch/powerpc/cpu/mpc8260/ether_fcc.c: Fix compile warning

Fix this:
ether_fcc.c: In function 'fec_initialize':
ether_fcc.c:390:15: warning: assignment from incompatible pointer type

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

arch/powerpc/cpu/mpc8260/ether_fcc.c

@@ -142,7 +142,7 @@ static RTXBD rtx __attribute__ ((aligned(8)));
 #error "rtx must be 64-bit aligned"
 #endif
 
-static int fec_send(struct eth_device* dev, volatile void *packet, int length)
+static int fec_send(struct eth_device *dev, void *packet, int length)
 {
     int i;
     int result = 0;