ravb: Update ravb_emac_init_gbeth()

This patch enables Receive/Transmit port of TOE and removes
the setting of promiscuous bit from EMAC configuration mode register.

This patch also update EMAC configuration mode comment from
"PAUSE prohibition" to "EMAC Mode: PAUSE prohibition; Duplex; TX;
RX; CRC Pass Through".

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>