usb: dwc3: gadget: Check for in-progress END_TRANSFER

While handling TRBs completion, if a END_TRANSFER command isn't
completed, don't kick new transfer or issue END_TRANSFER command.

Change-Id: Ic1d6b942c6c7993165d574dcc70078fb269365dd
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Git-commit: b6842d4938c3101cb54dc262a6a89a5445f8fba8
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


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