usb: isp1760: fix qtd fill length

When trying to send bulks bigger than the biggest block size
we need to split them over several qtd. Fix this limiting the
maximum qtd size to largest block size.

Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Link: https://lore.kernel.org/r/20210827131154.4151862-3-rui.silva@linaro.org


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