usb: isp1760: check maxpacketsize before using it

When checking if we need one more packet on a bulk pipe we may, even
though not probable at all, get there with a zero maxpacketsize.
In that case for sure no packet, no even a one more, will be
allocated.

This will clean the clang-analyzer warning:
drivers/usb/isp1760/isp1760-hcd.c:1856:38: warning: Division by zero [clang-analyzer-core.DivideZero]
                                && !(urb->transfer_buffer_length %

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Link: https://lore.kernel.org/r/20210819180929.1327349-3-rui.silva@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>