For the initial architecture submission, not all of the DMA ops were
implemented.  This patch adds the *map_page and *map_sg variants of the
DMA mapping ops.

This patch is currently of interest mainly to some drivers that haven't
been submitted upstream yet.
Signed-off-by: NJonas Bonn <jonas@southpole.se>

Simple DMA implementation.  Allows for allocation of coherent memory
(simply uncached) for DMA operations.
Signed-off-by: NJonas Bonn <jonas@southpole.se>
Reviewed-by: NArnd Bergmann <arnd@arndb.de>