The CXL driver provides a debugfs interface offering users the
ability to inject and clear poison to a memdev. Once a user has
injected up to the devices limit further injection requests fail
with ENXIO until a clear poison is issued.

Users may not have device specs in hand or may want to intentionally
hit the limit and then clear. Replace the usual ENXIO return status
with EBUSY so users can recognize this failure.
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Tested-by: Xingtao Yao <yaoxt.fnst@fujitsu.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Link: https://patch.msgid.link/825bd4c67fb55a4373c4182d999ad49d4e6b4fe7.1720316188.git.alison.schofield@intel.comSigned-off-by: Dave Jiang <dave.jiang@intel.com>