forcedeth: fix a few sparse warnings (variable shadowing)

This fixes the following sparse warnings:
drivers/net/ethernet/nvidia/forcedeth.c:2113:7: warning: symbol 'size' shadows an earlier one
drivers/net/ethernet/nvidia/forcedeth.c:2102:6: originally declared here
drivers/net/ethernet/nvidia/forcedeth.c:2155:7: warning: symbol 'size' shadows an earlier one
drivers/net/ethernet/nvidia/forcedeth.c:2102:6: originally declared here
drivers/net/ethernet/nvidia/forcedeth.c:2227:7: warning: symbol 'size' shadows an earlier one
drivers/net/ethernet/nvidia/forcedeth.c:2215:6: originally declared here
drivers/net/ethernet/nvidia/forcedeth.c:2271:7: warning: symbol 'size' shadows an earlier one
drivers/net/ethernet/nvidia/forcedeth.c:2215:6: originally declared here
drivers/net/ethernet/nvidia/forcedeth.c:2986:20: warning: symbol 'addr' shadows an earlier one
drivers/net/ethernet/nvidia/forcedeth.c:2963:6: originally declared here

Signed-off-by: David Decotigny <david.decotigny@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>