net: pcs: xpcs: move Wangxun VR_XS_PCS_DIG_CTRL1 configuration

According to commits 2a22b7ae ("net: pcs: xpcs: adapt Wangxun NICs
for SGMII mode") and 2deea43f ("net: pcs: xpcs: add 1000BASE-X AN
interrupt support"), Wangxun devices need special VR_XS_PCS_DIG_CTRL1
settings for SGMII and 1000BASE-X. Both SGMII and 1000BASE-X use the
same settings.

Rather than placing these in the individual xpcs_config_*() functions,
move it to where we already test for the Wangxun devices in
xpcs_do_config().

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>