e1000: remove unneeded conversion to bool

The '==' expression itself is bool, no need to convert it to bool again.
This fixes the following coccicheck warning:

drivers/net/ethernet/intel/e1000/e1000_main.c:1479:44-49: WARNING:
conversion to bool not needed here

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>