net: mvpp2: 10G modes aren't supported on all ports

[ Upstream commit 006791772084383de779ef29f2e06f3a6e111e7d ]

The mvpp2_phylink_validate() function sets all modes that are
supported by a given PPv2 port. A recent change made all ports to
advertise they support 10G modes in certain cases. This is not true,
as only the port #0 can do so. This patch fixes it.

Fixes: 01b3fd5ac97c ("net: mvpp2: fix detection of 10G SFP modules")
Cc: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>