enic: Clean up: remove enic_dev_stats_clear

Remove function enic_dev_stats_clear and its reference in enic device
init code. Firmware clears device stats on device open. So, no need for
the driver to do it again.

Signed-off-by: Scott Feldman <scofeldm@cisco.com>
Signed-off-by: Roopa Prabhu <roprabhu@cisco.com>
Signed-off-by: Vasanthy Kolluri <vkolluri@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>