ASoC: SOF: Intel: hda-ipc: simplify handling of IPC IRQ

When using a shared IRQ between IPC interrupt and stream IOC interrupt,
the interrupt handlers need to check the interrupt source before
scheduling their respective IRQ threads. In the case of IPC handler, it
should check if it is an IPC interrupt before waking up the IPC IRQ
thread.

The IPC IRQ thread, once scheduled, does not need to check the IRQ
source again. So, remove the superfluous check in the thread. Remove the
irq_status field from snd_sof_dev struct also as it is no longer needed.

Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>