2n-grc: CX5 had better performance than CX7

[vrpolakatcisco]

Baseline tests in trending: [0], both using the same dpdk plugin with mlx5 driver.
CSIT no longer seems to compare NICs thoroughly (for example 2n-zn2 tests Intel xxv710, other testbeds test E810, with no overlap on the same testbed), so it is not clear whether such differences are normal or worth fixing.

[0] https://csit.fd.io/trending/#eNrVlt1ugyAYhq_GnSxfUlnBnexgnffRILJqAkqAtXZXP3BL0aZ1M5t2HvgD3_8T8gZja823hounCG-iZBOhpMzdK3p4vnefvVKAKthpBvFqteNIxazBmFCQosFQqjWQdQYxA24Lv3JPRg0HqbXPgl58lvzN9lIGiyqOwXK9UAigmtMQ4aoFk-WmU6bfT_B61VRyU77z4OomCHbmeARTzPr57VF1rF9DJmnrMR4egeQxwCN-Z1Z4ZBDeqZ9BeG6CW8ATqHPw3CrLfaeSMqGrmfgJNIDvrKX_eP7OETZsxsP3HbzPZm6NDZ0GSvac2glF71KlxaveFXwTyN44fAvRvYv4phK-MQSXpHw_gvh76ftLfPNoH07vqlrL9t7n_k1RH8DqkgrTbrngduG9cfoBZii9Sw