net/mlx5e: Fix wraparound in rate limiting for values above 255 Gbps

net/mlx5e: Fix wraparound in rate limiting for values above 255 Gbps

Add validation to reject rates exceeding 255 Gbps that would overflow
the 8 bits max bandwidth field.

Fixes: d8880795dabf ("net/mlx5e: Implement DCBNL IEEE max rate")
Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Nimrod Oren <noren@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1762681073-1084058-5-git-send-email-tariqt@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>