net/mlx5e: Drop cqe_bcnt32 from mlx5e_skb_from_cqe_mpwrq_linear

The packet size in mlx5e_skb_from_cqe_mpwrq_linear can't overflow u16,
since the maximum packet size in linear striding RQ is 2^13 bytes. Drop
the unneeded u32 variable.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>