Revert "usb: dwc3: Remove the checks of -ENOSYS"

This reverts commit df22ecc4.

If CONFIG_GENERIC_PHY is not enabled, then the devm_phy_get() returns
-ENOSYS. Don't remove this check.

Fixes: df22ecc4 ("usb: dwc3: Remove the checks of -ENOSYS")
Cc: Kushagra Verma <kushagra765@outlook.com>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/eb1df7ef954b5af093c0528982db52a41df18615.1655255152.git.Thinh.Nguyen@synopsys.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>