net: hibmcge: Add support for dump statistics

The driver supports many hw statistics. This patch supports
dump statistics through ethtool_ops and ndo.get_stats64().

The type of hw statistics register is u32,
To prevent the statistics register from overflowing,
the driver dump the statistics every 30 seconds.
in a scheduled task.

Signed-off-by: Jijie Shao <shaojijie@huawei.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>