net: fman: Don't pass comm_mode to enable/disable

mac_priv_s->enable() and ->disable() are always called with
a comm_mode of COMM_MODE_RX_AND_TX. Remove this parameter, and refactor
the macs appropriately.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Acked-by: Camelia Groza <camelia.groza@nxp.com>
Tested-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>