drm/i915/mtl: Apply notify_guc to all GTs

drm/i915/mtl: Apply notify_guc to all GTs

Handle platforms with multiple GTs by iterate over all GTs.
Add a Fixes commit so this gets propagated for MTL support.

Fixes: 213c43676beb ("drm/i915/mtl: Remove the 'force_probe' requirement for Meteor Lake")
Suggested-by: John Harrison <john.c.harrison@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231025102826.16955-1-nirmoy.das@intel.com