usb: dwc3: gadget: Don't setup more than requested

[ Upstream commit 5d187c0454ef4c5e046a81af36882d4d515922ec ]

The SG list may be set up with entry size more than the requested
length. Check the usb_request->length and make sure that we don't setup
the TRBs to send/receive more than requested. This case may occur when
the SG entry is allocated up to a certain minimum size, but the request
length is less than that. It can also occur when the request is reused
for a different request length.

Cc: <stable@vger.kernel.org> # v4.18+
Fixes: a31e63b6 ("usb: dwc3: gadget: Correct handling of scattergather lists")
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>