drm/xe: Document nested struct members according to guidelines

Document nested struct members with full names as described in
Documentation/doc-guide/kernel-doc.rst.

For this documentation we allow a column width of 100 to make
it more readable.

This fixes warnings similar to:
drivers/gpu/drm/xe/xe_lrc_types.h:45: warning: Excess struct member 'size' description in 'xe_lrc'

v2:
- Only change the documentation, not the member.

v3:
- Fix the commit message wording.

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240123153147.27305-1-thomas.hellstrom@linux.intel.com

drm/xe: Rename engine to exec_queue

Engine was inappropriately used to refer to execution queues and it
also created some confusion with hardware engines. Where it applies
the exec_queue variable name is changed to q and comments are also
updated.

Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/162
Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drm/xe: fix kernel-doc issues

drivers/gpu/drm/xe/xe_guc_submit_types.h:47: warning: cannot understand
function prototype: 'struct guc_submit_parallel_scratch '

drivers/gpu/drm/xe/xe_devcoredump_types.h:38: warning: Function
parameter or member 'ct' not described in 'xe_devcoredump_snapshot'

CI doesn't appear to be running BAT anymore, assuming this is caused by
the CI.Hooks now failing due to above warnings.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drm/xe: Convert GuC Engine print to snapshot capture and print.

The goal is to allow for a snapshot capture to be taken at the time
of the crash, while the print out can happen at a later time through
the exposed devcoredump virtual device.

v2: Handle memory allocation failures. (Matthew)
Do not use GFP_ATOMIC on cases like debugfs prints. (Matthew)
v3: checkpatch
v4: pending_list allocation needs to be atomic because of the
spin_lock. (Matthew)
get back to GFP_ATOMIC only. (lockdep).

Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>

drm/xe: Introduce guc_submit_types.h with relevant structs.

These structs and definitions are only used for the guc_submit
and they were added specifically for the parallel submission.

While doing that also delete the unused struct guc_wq_item.

v2: checkpatch fixes.

Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>