staging: dwc2: don't pass IRQ_LEVEL to devm_request_irq

It seems this flag is intended to pass to irq_set_status_flags, not
request_irq, and is not available on all architectures. Its value
corresponds to IRQF_PROBE_SHARED, which shouldn't be needed for this
driver, so removing this flag should be safe.

Signed-off-by: Matthijs Kooijman <matthijs@stdin.nl>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>