Switch from contiguous raw scatterlist to use scatterlist table api instead, fixes memory alloc failure when host memory gets fragmented enough to not be able to allocate enough memory for a contiguous scatterlist.
Don't increment ISR count if no outstanding commands, prevents test failure due to race between reaped completion, unmasking interrupts, and device canceling interrupt, sometimes spurious interrupt may occur that arrive the moment interrupts are unmasked.