staging: dwc2: fix thinko in dwc2_fill_host_dma_desc()

The check against MAX_DMA_DESC_SIZE didn't make sense, fix it

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>