UPSTREAM: usb: dwc3: remove num_event_buffers

UPSTREAM: usb: dwc3: remove num_event_buffers

We never, ever route any of the other event buffers
so we might as well drop support for them.

Until someone has a real, proper benefit for
multiple event buffers, we will rely on a single
one. This also helps reduce memory footprint of
dwc3.ko which won't allocate memory for the extra
event buffers.

Change-Id: I70bf36abecc422e59e90a89bb3438be6de0f8ef1
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Wu Liang feng <wulf@rock-chips.com>
(cherry picked from commit 660e9bde74d6915227d7ee3485b11e5f52637b26)