usb: Add delay before checking request status

USB H/W generates endpoint completion interrupt when data is
received on any endpoint. Upon ep complete interrupt, S/W
checks request status and unlinks the request from h/w queue.
Sometimes h/w is taking around 200us to update ep data after
generating the interrupt which is causing data stall when
there is huge traffic on any endpoint. Delay checking USB
request for 200us after endpoint completion interrupt

Signed-off-by: Vamsi Krishna <vskrishn@codeaurora.org>
Signed-off-by: Zhoulu Luo <zluo@codeaurora.org>