According to xHCI ch4.20 Scratchpad Buffers, the Scratchpad
Buffer needs to be zeroed.
	...
	The following operations take place to allocate
       	Scratchpad Buffers to the xHC:
	...
		b. Software clears the Scratchpad Buffer to '0'
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
        xhci->dcbaa->dev_context_ptrs[0] = cpu_to_le64(xhci->scratchpad->sp_dma);
        for (i = 0; i < num_sp; i++) {
                dma_addr_t dma;
-               void *buf = dma_alloc_coherent(dev, xhci->page_size, &dma,
+               void *buf = dma_zalloc_coherent(dev, xhci->page_size, &dma,
                                flags);
                if (!buf)
                        goto fail_sp4;