USB: ci13xxx_udc: Add timeout of 100ms for endpoint flush loop

Currently completion of endpoint flush operation is checked after
setting that endpoint bit with ENDPTFLUSH register and polling the
same to get it clear. It has been observed that sometime this flush
operation takes huge amount of time which results into watchdog
timeout issue due to this busy loop without any time-out. Hence add
time-out of 100ms for endpoint flush operation completion and also
add 100us delay before checking ENDPTFLUSH register for endpoint bit
clear or not.

Also print important usb status register and flushed endpoint dtds
at the time of issue.

CRs-Fixed: 409382
Change-Id: I7ae57cc436077f8a03051b92750bdca9a571da2b
Signed-off-by: Mayank Rana <mrana@codeaurora.org>