drivers/net: normalize TX_TIMEOUT

Some network drivers use old TX_TIMEOUT definitions, assuming HZ=100 of
old kernels.

Convert these definitions to include HZ, since HZ can be 1000 these
days.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>