drm/i915/guc: Rename i915_guc_submission.c|h to intel_guc_submission.c|h

drm/i915/guc: Rename i915_guc_submission.c|h to intel_guc_submission.c|h

With all component structures and functions named appropriately, change
the names of GuC submission source files. There were bunch of style issues
in guc_submission.c that are highlighted now by checkpatch. Fix those.
Update name in Documentation/gpu. (Joonas)

v2: Rebase.

v3: Rebase.

Signed-off-by: Sagar Arun Kamble <[email protected]>
Cc: Michal Wajdeczko <[email protected]>
Cc: Michal Winiarski <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Acked-by: Chris Wilson <[email protected]>
Acked-by: Joonas Lahtinen <[email protected]>
Acked-by: Oscar Mateo <[email protected]>
Reviewed-by: Michal Wajdeczko <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Chris Wilson <[email protected]>