net: phy: genphy_10g_driver: Avoid NULL pointer dereference

This driver got missed during the recent change of .features from a
u32 to a pointer to a Linux bitmap. Change the initialisation from 0
to PHY_10GBIT_FEATURES so removing the danger of a NULL pointer
dereference.

Fixes: 719655a1 ("net: phy: Replace phy driver features u32 with link_mode bitmap")
Reported-by: Jose Abreu <jose.abreu@synopsys.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>