usb: dwc3: qcom: only parse 'maximum-speed' once

Add a temporary variable to the interconnect-initialisation helper to
avoid parsing and decoding the 'maximum-speed' devicetree property
twice.

Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20220805074500.21469-2-johan+linaro@kernel.org


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