dwc3-msm: Block doorbell to GSI from USB wrapper

It is required to block doorbell to GSI to avoid USB wrapper
from ringing doorbell before queuing stop xfer command to GSI
endpoint as part of stopping controller. Otherwise USB wrapper
is accessing IPA doorbell register while clocks are off after
restarting USB controller. Hence fix it by blocking doorbell
to GSI for avoiding this issue before queueing endxfer command
to GSI endpoint.

Change-Id: If926386462423f60d5c2535d766b6cb9ba59ea6f
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>
Signed-off-by: Mayank Rana <mrana@codeaurora.org>