net/mlx5: sparse: warning: incorrect type in assignment

drivers/net/ethernet/mellanox/mlx5/core/diag/fw_tracer.c:191:13:
sparse: warning: incorrect type in assignment (different base types)

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Moshe Shemesh <moshe@mellanox.com>