usb: dwc3: qcom: clean up suspend callbacks

Clean up the suspend callbacks by separating the error and success paths
to improve readability.

Also drop a related redundant initialisation.

Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20220804151001.23612-10-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>