Revert "usb: dwc3: Reset the transfer resource index on SET_INTERFACE"

commit a0c76018 ("usb: dwc3: Reset the transfer resource index
on SET_INTERFACE") was resetting the start_config_issued flag on
receiving SetInterface request. But in cases where transfer resource
index is shared between two endpoints and if both are trying to do a
transfer then transfer on one of the endpoints will fail, since the
transfer resource index will be acquired by the first endpoint
and when the second endpoint tries to get the same transfer resource
index, it will fail and hence STARTTRANSFER command also fails on second
endpoint.
Reverting this change ensures endpoints get allocated with unique
transfer resource index.
CRs-fixed: 953585

Change-Id: I7800356e455900cc39b9463366275c68db777199
Signed-off-by: Azhar Shaikh <azhars@codeaurora.org>