net: phy: marvell10g: fix differentiation of 88X3310 from 88X3340

It seems that we cannot differentiate 88X3310 from 88X3340 by simply
looking at bit 3 of revision ID. This only works on revisions A0 and A1.
On revision B0, this bit is always 1.

Instead use the 3.d00d register for differentiation, since this register
contains information about number of ports on the device.

Fixes: 9885d016 ("net: phy: marvell10g: add separate structure for 88X3340")
Signed-off-by: Marek Behún <kabel@kernel.org>
Reported-by: Matteo Croce <mcroce@linux.microsoft.com>
Tested-by: Matteo Croce <mcroce@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>