sky2: enable rx/tx in sky2_phy_reinit()

sky2_phy_reinit is called by the ethtool helpers sky2_set_settings,
sky2_nway_reset and sky2_set_pauseparam when netif_running.

However, at the end of sky2_phy_init GM_GP_CTRL has GM_GPCR_RX_ENA and
GM_GPCR_TX_ENA cleared. So, doing these commands causes the device to
stop working:

$ ethtool -r eth0
$ ethtool -A eth0 autoneg off

Fix this issue by enabling Rx/Tx after running sky2_phy_init in
sky2_phy_reinit.

Signed-off-by: Brandon Philips <bphilips@suse.de>
Tested-by: Brandon Philips <bphilips@suse.de>
Cc: stable@kernel.org
Tested-by: Mike McCormack <mikem@ring3k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>