usb: dwc3: gadget: only interrupt on short if short_not_ok is set

We don't need to know about short packets unless
gadget driver told us it's not ok to see them on the
bus. In the normal situation we can continue
processing the list of requests if we get a Short
packet.

Also, note that we're making sure ISP is only set
for OUT endpoints, where that setting is valid.

Change-Id: Iedf1a4a6e8e8193aa4f3ec14a8581cf9c8eea50f
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Git-commit: c9508c8c50f9ec6fc3e7e823f35c76fafba7e929
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Mayank Rana <mrana@codeaurora.org>