USB: ci13xxx_udc: Skip flushing endpoints upon failure

Flushing an endpoint involve polling ENDPTFLUSH and ENDPTSTAT
registers.  The worst case timeout is 100 msec for each endpoint.
The reason for failure is unknown.  When flushing an endpoint
fails, successive flushing of remaining endpoints are also failing.
Hence skip flushing remaining endpoints.  Reset this condition
upon USB bus reset.

(cherry picked from commit 2a630fb9b83b31e607ef61f3b61959cc1b095349)

CRs-Fixed: 445916
Change-Id: I54cf860c0d290ffa3fc0d7e41af32b4be48937ef
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>