drm/i915: Initialize dkl_phy spin lock from display code path

Start moving the initialization of display locks from
i915_driver_early_probe().
Display locks should be initialized from display-only code paths.

It was also agreed that if a variable is only used in one file, it
should be initialized only in that file, so intel_dkl_phy_init() was
added.

v2:
- added intel_display_locks_init()

v3:
- rebased

v4:
- dropped intel_display_locks_init()

v5:
- moved intel_dkl_phy_init() to the beginning of file

Cc: intel-gfx@lists.freedesktop.org
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230420170558.35398-1-jose.souza@intel.com