dmaengine: idxd: Remove unused pointer and macro

The pointer 'extern struct kmem_cache *idxd_desc_pool' and the macro
'#define IDXD_ALLOCATED_BATCH_SIZE 128U' were introduced in commit
bfe1d560 ("dmaengine: idxd: Init and probe for Intel data
accelerators") but they were never used.

Signed-off-by: Eder Zulian <ezulian@redhat.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20250408173829.892317-1-ezulian@redhat.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>