drivers/net/atl1e: fix sparse warnings: fix signedness

Fix this sparse warnings:
  drivers/net/atl1e/atl1e_main.c:716:39: warning: incorrect type in argument 2 (different signedness)
  drivers/net/atl1e/atl1e_param.c:57:1: warning: incorrect type in initializer (different signedness)
  drivers/net/atl1e/atl1e_param.c:68:1: warning: incorrect type in initializer (different signedness)
  drivers/net/atl1e/atl1e_param.c:81:1: warning: incorrect type in initializer (different signedness)
  drivers/net/atl1e/atl1e_param.c:92:1: warning: incorrect type in initializer (different signedness)

Signed-off-by: Hannes Eder <hannes@hanneseder.net>
Signed-off-by: David S. Miller <davem@davemloft.net>