Add new debugfs_add_region_item along with a generic wrapper
snd_sof_debugfs_add_region_item() to abstract away the DSP regions related
debugfs support.

At the same commit add iomem based generic implementation for the new ops
Signed-off-by: NPeter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: NDaniel Baluta <daniel.baluta@gmail.com>
Reviewed-by: NRanjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: NGuennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Link: https://lore.kernel.org/r/20210915122116.18317-9-peter.ujfalusi@linux.intel.comSigned-off-by: NMark Brown <broonie@kernel.org>