UPSTREAM: usb: dwc3: gadget: always enable CSP

UPSTREAM: usb: dwc3: gadget: always enable CSP

CSP bit of TRB Control is useful for protocols such
CDC EEM/ECM/NCM where we're transferring in blocks
of MTU-sized requests (usually MTU is 1500 bytes).

We know we will always have a short packet after two
(for HS) wMaxPacketSize packets and, usually, we
will have a long(-ish) queue of requests (for our
g_ether gadget, we have at least 10
requests).

Instead of always stopping the queue processing to
interrupt, giveback and restart, let's tell dwc3 to
interrupt but continue processing following request
if we have anything already pending in the queue.

This gave me a considerable improvement of 40% on my
test setup.

Change-Id: I02ba152fff9cacad4ffabb3c03a70b06774c09ee
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Wu Liang feng <wulf@rock-chips.com>
(cherry picked from commit ca4d44ea2a91b922e1514f5ed77f6bcf3657fd67)