Hdmi audio driver based on the child platform device
created by gfx driver is implemented.
This audio driver is derived from legacy intel
hdmi audio driver.

The interfaces for interaction between gfx and audio
are updated and the driver implementation updated to
derive interrupts in its own address space based on
irq chip framework

The changes to calculate sub-period positions was triggered
by David Henningsson <david.henningsson@canonical.com> and is
accomodated in this patch
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Jerome Anand <jerome.anand@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>