The sst-firmware was also using own method to do 32bit copy, turns out we have a
kernel API so use that instead

[For BYT]
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>