drivers/usb/eth/smsc95xx.c: Fix GCC 4.6 warning

Fix:
smsc95xx.c: In function 'smsc95xx_eth_get_info':
smsc95xx.c:869:12: warning: assignment from incompatible pointer type
[enabled by default]

Signed-off-by: Anatolij Gustschin <agust@denx.de>