drm/i915/mtl: Use primary GT's irq lock for media GT

drm/i915/mtl: Use primary GT's irq lock for media GT

When we hook up interrupts (in the next patch), interrupts for the media
GT are still processed as part of the primary GT's interrupt flow.  As
such, we should share the same IRQ lock with the primary GT.  Let's
convert gt->irq_lock into a pointer and just point the media GT's
instance at the same lock the primary GT is using.

v2:
 - Point media's gt->irq_lock at the primary GT lock properly.  (Daniele)
 - Fix jump target for intel_root_gt_init_early errors.  (Daniele)

Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220906234934.3655440-14-matthew.d.roper@intel.com
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>