dmaengine: idxd: iax bus removal

There is no need to have an additional bus for the IAX device. The removal
of IAX will change user ABI as /sys/bus/iax will no longer exist.
The iax device will be moved to the dsa bus. The device id for dsa and
iax will now be combined rather than unique for each device type in order
to accommodate the iax devices. This is in preparation for fixing the
sub-driver code for idxd. There's no hardware deployment for Sapphire
Rapids platform yet, which means that users have no reason to have
developed scripts against this ABI. There is some exposure to
released versions of accel-config, but those are being fixed up and
an accel-config upgrade is reasonable to get IAX support. As far as
accel-config is concerned IAX support starts when these devices appear
under /sys/bus/dsa, and old accel-config just assumes that an empty /
missing /sys/bus/iax just means a lack of platform support.

Fixes: f25b4638

 ("dmaengine: idxd: add IAX configuration support in the IDXD driver")
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/161852988298.2203940.4529909758034944428.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>