Input: wm97xx-core - fix race on PHY init

The chip phy_init() function must be called before the dig_enable() function
but dig_enable() is called when the device is opened and we only call
phy_init() after having reigstered the device, meaning the two can race.
Fix this by doing the phy_init() before we register the input device.

Thanks to Rodolfo Giometti <giometti@enneenne.com> for the report.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>