dmaengine: idxd: assign all engines to group 0 in IAA defaults

The IAA device defaults only assigned engine 0 to group 0, leaving
engines 1 through max_engines-1 unassigned (group_id = -1). This means
that by default only a single engine processed descriptors, limiting
throughput to one engine's capacity.

Assign all available engines to group 0 so that the full hardware
parallelism is used out of the box without requiring manual
accel-config setup.

Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20260805-iaa-crypto-fixes-zswap-v2-1-55c02694f499@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>