net: phy: et1011c: Remove incorrect missing 1000 Half

The driver indicates it can do 10/100 full and half duplex, plus 1G
Full. The datasheet indicates 1G half is also supported. So make use
of the standard PHY_GBIT_FEATURES.

It could be, this was added because there is a MAC which does not
support 1G half. Bit this is the wrong place to enforce this.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>