pcnet32: round off carrier watch timer

The link check watchdog timer on this driver fires every two seconds, but
since not aligned it causes extra wakeups. It is more important on this
driver than most because it is the hardware that is emulated by default
when using network interfaces on VMware.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>