compress: add the core file

This patch ads core.c, the file which implements the ioctls and
registers the devices

Change-Id: I30a1d8b561ecd15b6a862d6948368394edd49665
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Asish Bhattacharya <asishb@codeaurora.org>