The DSP may send the same interrupt multiple times before it's handled
in the interrupt thread. Rather than masking it in the thread, mask it
in the handler directly.

This patch also removes useless checks that cannot happen, and masks
that are set don't need to be re-tested.
Suggested-by: Keyon Jie <yang.jie@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
BugLink: https://github.com/thesofproject/linux/issues/1492
Link: https://lore.kernel.org/r/20200526203640.25980-8-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>