net: dsa: mt7530: move MT753X_MTRAP operations for MT7530

On MT7530, the media-independent interfaces of port 5 and 6 are controlled
by the MT7530_P5_DIS and MT7530_P6_DIS bits of the hardware trap. Deal with
these bits only when the relevant port is being enabled or disabled. This
ensures that these ports will be disabled when they are not in use.

Do not set MT7530_CHG_TRAP on mt7530_setup_port5() as that's already being
done on mt7530_setup().

Instead of globally setting MT7530_P5_MAC_SEL, clear it, then set it only
on the appropriate case.

If PHY muxing is detected, clear MT7530_P5_DIS before calling
mt7530_setup_port5().

Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Signed-off-by: David S. Miller <davem@davemloft.net>