drm/xe/guc: Add more GuC CT states

The Guc CT has more than enabled / disables states rather it has 4. The
4 states are not initialized, disabled, stopped, and enabled. Change the
code to reflect this. These states will enable proper return codes from
functions and therefore enable proper error messages.

v2:
- s/XE_GUC_CT_STATE_DROP_MESSAGES/XE_GUC_CT_STATE_STOPPED (Michal)
- Add assert for CT being initialized (Michal)
- Fix kernel for CT state enum (Michal)

v3:
- Kernel doc (Michal)
- s/reiecved/received (Michal)
- assert CT state not initialized in xe_guc_ct_init (Michal)
- add argument xe_guc_ct_set_state to clear g2h (Michal)

v4:
- Drop clear_outstanding_g2h argument (Michal)

v5:
- Move xa_destroy outside of fast lock (CI)

Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Tejas Upadhyay <tejas.upadhyay@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240122210156.1517444-2-matthew.brost@intel.com