net/mlx5: Fix wrong size allocation for QoS ETC TC regitster

[ Upstream commit d14fcb8d877caf1b8d6bd65d444bf62b21f2070c ]

The driver allocates wrong size (due to wrong struct name) when issuing
a query/set request to NIC's register.

Fixes: d8880795 ("net/mlx5e: Implement DCBNL IEEE max rate")
Signed-off-by: Shay Agroskin <shayag@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>