There is a lot of duplicate code when processing IPC firmware ready
notification and creating memory windows.

First step in reducing the code duplication is to introduce generic
functions:
	* sof_get_windows
	* sof_fw_ready
that will replace, in the first step, the specific implementation related
to baytrail related platforms:
	* byt_get_windows
	* byt_fw_ready

So we are basically moving code from intel/byt.c to loader.c keeping
in mind that mbox_offset is a per platform constant so we need to
use newly introduced snd_sof_dsp_get_mailbox_offset /
snd_sof_dsp_get_window_offset in order to get the correct
mbox offset / window offset value.

Also, bar is a per platform constant so we use snd_sof_dsp_get_bar_index
instead of the hardcoded BYT_DSP_BAR.
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20190807150203.26359-5-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>