usb: ehci-orion: fix probe for !GENERIC_PHY

Commit d445913c ("usb: ehci-orion: add optional PHY support")
added support for optional phys, but devm_phy_optional_get returns
-ENOSYS if GENERIC_PHY is not enabled.

This causes probe failures, even when there are no phys specified:

[    1.443365] orion-ehci f1058000.usb: init f1058000.usb fail, -38
[    1.449403] orion-ehci: probe of f1058000.usb failed with error -38

Similar to dwc3, treat -ENOSYS as no phy.

Fixes: d445913c

 ("usb: ehci-orion: add optional PHY support")

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>