net/mlx5: Fix uininitialized pointer read on pointer attr

Currently the error exit path err_free kfree's attr. In the case where
flow and parse_attr failed to be allocated this return path will free
the uninitialized pointer attr, which is not correct.  In the other
case where attr fails to allocate attr does not need to be freed. So
in both error exits via err_free attr should not be freed, so remove
it.

Addresses-Coverity: ("Uninitialized pointer read")
Fixes: ff7ea04a ("net/mlx5e: Fix potential null pointer dereference")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>