phy-core: Don't propagate -ENOSUPP from phy_pm_runtime_get_sync to caller

The phy-core allows phy_init and phy_power_on to be called multiple times,
but before this patch -ENOSUPP from phy_pm_runtime_get_sync would be
propagated to the caller for the 2nd and later calls.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>