benet: Fix compile warnnings in drivers/net/benet/be_ethtool.c

Fix the following warnings:

be_ethtool.c:493: warning: integer constant is too large for 'long' type
be_ethtool.c:493: warning: integer constant is too large for 'long' type

Signed-off-by: Zhitong Wang <zhitong.wangzt@alibaba-inc.com>
Acked-by: Ajit Khaparde <ajitk@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>