dma_direct_set_offset has been moved from dma-mapping.h to
dma-map-ops.h, but our driver hasn't been updated resulting in a build
breakage. Let's change the header to fix the build.

Fixes: 16fee29b ("dma-mapping: remove the dma_direct_set_offset export")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20201124103546.839711-1-maxime@cerno.tech'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>