spi: spi-fsl-dspi: fix native data copy

ColdFire is a big-endian cpu with a big-endian dspi hw module,
so, it uses native access, but memcpy breaks the endianness.

So, if i understand properly, by native copy we would mean
be(cpu)->be(dspi) or le(cpu)->le(dspi) accesses, so my fix
shouldn't break anything, but i couldn't test it on LS family,
so every test is really appreciated.

Fixes: 53fadb4d ("spi: spi-fsl-dspi: Simplify bytes_per_word gymnastics")
Signed-off-by: Angelo Dureghello <angelo.dureghello@timesys.com>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20200529195756.184677-1-angelo.dureghello@timesys.com


Signed-off-by: Mark Brown <broonie@kernel.org>