net/mlx5: fix imissed counter overflow

net/mlx5: fix imissed counter overflow

The Hw counters is defined as 32bit unsigned value and read from
the sysfs. Firstly read the base value while application start,
then fetch the new value while do query and minus the base value.
If the new value is less than base value, will result in a
negative value and convert to the big value as unsigned 64bit.

PMD add xstats field to store the last successfully read counter,
use it if failed to read hw counter from sysfs.
PMD also record the last output value to handle the wrap around case,
if overflow happened, increase the wrap count by 1 and save into the
higher 32bit, and update the new value into lower 32bit, finally
return the 64bit counter value.

Fixes: ce9494d76c47 ("net/mlx5: report imissed statistics")
Cc: stable@dpdk.org
Signed-off-by: Jiawei Wang <jiaweiw@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>