fsl/fman: Remove a useless call to 'dev_set_drvdata()'

Commit c6e26ea8

 ("dpaa_eth: change device used") has removed usage of
'dev_set_drvdata()' in the 'mac_probe() function.

This call should also be axed.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>