usb: dwc3: omap: Use devm_regulator_get_optional()

The 'vbus-supply' regulator is optional, so use
devm_regulator_get_optional() instead of checking for property presence
first.

While here, rework the error handling to use dev_err_probe() which
handles deferred probe correctly without an error message.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20241231164456.262581-1-robh@kernel.org


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