usb: dwc3: Avoid CLR block DB if run/stop is cleared

It is required to SET block doorbell to GSI to avoid USB wrapper
from ringing doorbell before queuing stop xfer command to GSI
endpoint as part of stopping controller and CLR block doorbell to
GSI after queuing start xfer command to GSI endpoint.

Since ipa_work_handler runs in workqueue context there is a possiblity
that CLR block doorbell will happen even after run/stop is
cleared which may lead to SMMU fault. Avoid this by adding a check
for pullups_connected before clearing block doorbell.

Change-Id: Iedb8a96da197834169bdabae6381c974d50c95de
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>