net: ti: icssg-prueth: Remove duplicate cleanup calls in emac_ndo_stop()

Remove the duplicate calls to prueth_emac_stop() and
prueth_cleanup_tx_chns() in emac_ndo_stop().

Signed-off-by: Diogo Ivo <diogo.ivo@siemens.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: MD Danish Anwar <danishanwar@ti.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>