Kick in scatterlist DMA support for the MMC/SD driver, with NR_SG=16
so this will usually do as much I/O per IRQ as it would using the
block bounce buffer logic.  Each DMA segment is most often a single
page; larger segments happen too, over 15% on some loads.  It's also
common for all the extra reload slots to be used, though again short
scatterlists (one or two entries) are most common.

Unrelated:  add my copyright, and remove the revision history comments
(which is the standard policy for mainline code).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>