Use a single cache for all sed allocations. No need to make it per
channel. This also avoids the slub_debug warnings for multiple caches
with the same name.
Switching to dmam_pool_create() to fix leaking the dma pools on
initialization failure and lets us kill ioat3_dma_remove().
Cc: Dave Jiang <dave.jiang@intel.com> Acked-by: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>