dmaengine: idxd: remove gen cap field per spec 1.2 update

dmaengine: idxd: remove gen cap field per spec 1.2 update

Remove max_descs_per_engine field. The recently released DSA spec 1.2 [1]
has removed this field and made it reserved.

[1]: https://software.intel.com/content/dam/develop/external/us/en/documents-tps/341204-intel-data-streaming-accelerator-spec.pdf

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/163406167978.1303649.1798682437841822837.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>