xhci: update bounce buffer with correct sg num

This change fixes a data corruption issue occurred on USB hard disk for
the case that bounce buffer is used during transferring data.

While updating data between sg list and bounce buffer, current
implementation passes mapped sg number (urb->num_mapped_sgs) to
sg_pcopy_from_buffer() and sg_pcopy_to_buffer(). This causes data
not get copied if target buffer is located in the elements after
mapped sg elements. This change passes sg number for full list to
fix issue.

Besides, for copying data from bounce buffer, calling dma_unmap_single()
on the bounce buffer before copying data to sg list can avoid cache issue.

Fixes: f9c589e1 ("xhci: TD-fragment, align the unsplittable case with a bounce buffer")
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: Henry Lin <henryl@nvidia.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>