Some controller as the ColdFire eshdc may require an endianness
byte swap, because DMA read endianness is not configurable.

Facilitate using the bounce buffer for this by adding
->copy_to_bounce_buffer().
Signed-off-by: NAngelo Dureghello <angelo.dureghello@timesys.com>
Acked-by: NAdrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20200518191742.1251440-2-angelo.dureghello@timesys.comSigned-off-by: NUlf Hansson <ulf.hansson@linaro.org>