net/mlx5: fix meter EIR calculation

net/mlx5: fix meter EIR calculation

Before the yellow color policy was supported, the only supported
profile of metering is RFC2697 and EIR is not part of the profile.
When creating a meter with this profile, the EIR part was always
zero.

After the yellow color policy supported and RFC2698 & 4115 support
was introduced, EIR is relevant and should be calculated. Usually
the EIR could not be zero and the formula for calculating CIR
mantissa & exponent could be reused.

The EIR could be 0 and then only green and red colors will be
supported from the specification. Both the mantissa and exponent
parts should be set to 0. Currently, the formula wrongly sets
non-zero values for the EIR=0 case.

Setting the mantissa and the exponent parts to zeros when EIR is 0
will solve the issue.

Fixes: 33a7493c8df8 ("net/mlx5: support meter for trTCM profiles")
Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>