drm/i915/guc: Add onion teardown to the GuC setup

Starting with intel_guc_loader, down to intel_guc_submission
and finally to intel_guc_log.

v2:
  - Null execbuf client outside guc_client_free (Daniele)
  - Assert if things try to get allocated twice (Daniele/Joonas)
  - Null guc->log.buf_addr when destroyed (Daniele)
  - Newline between returning success and error labels (Joonas)
  - Remove some unnecessary comments (Joonas)
  - Keep guc_log_create_extras naming convention (Joonas)
  - Helper function guc_log_has_extras (Joonas)
  - No need for separate relay_channel create/destroy. It's just another extra.
  - No need to nullify guc->log.flush_wq when destroyed (Joonas)
  - Hoist the check for has_extras out of guc_log_create_extras (Joonas)
  - Try to do i915_guc_log_register/unregister calls (kind of) symmetric (Daniele)
  - Make sure initel_guc_fini is not called before init is ever called (Daniele)

v3:
  - Remove unnecessary parenthesis (Joonas)
  - Check for logs enabled on debugfs registration
  - Rebase on top of Tvrtko's "Fix request re-submission after reset"

v4:
  - Rebased
  - Comment around enabling/disabling interrupts inside GuC logging (Joonas)

Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>