net: phy: marvell10g: fix the PHY id mask

The Marvell 10G PHY driver supports different hardware revisions, which
have their bits 3..0 differing. To get the correct revision number these
bits should be ignored. This patch fixes this by using the already
defined MARVELL_PHY_ID_MASK (0xfffffff0) instead of the custom
0xffffffff mask.

Fixes: 20b2af32

 ("net: phy: add Marvell Alaska X 88X3310 10Gigabit PHY support")
Suggested-by: Yan Markman <ymarkman@marvell.com>
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>