The mac statistics add pause/pfc durations in device version V3, we can
get total active cycle of pause/pfc from these durations.

As driver gets register number from firmware to calculate desc number to
query mac statistics, it needs to set mac statistics extended enable bit
in firmware command 0x701A to tell firmware that driver supports extended
mac statistics, otherwise firmware only returns register number of
version V1.

As pause/pfc durations are not supported by hardware of old version, they
should not been shown in command "ethtool -S ethX" in this case, so add
checking max register number of each mac statistic in their version.
If the max register number of one mac statistic is greater than register
number got from firmware, it means hardware does not support this mac
statistic, so ignore this statistic when get string and data of mac
statistic.
Signed-off-by: NGuangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>