drm/i915/dp: Use an intel_connector pointer everywhere

drm/i915/dp: Use an intel_connector pointer everywhere

Following the convention, convert intel_dp.c to use an intel_connector
pointer everywhere, calling this pointer connector. If the intel
connector must be casted from a drm_connector, call this pointer
_connector and use this pointer only for the casting.

v2: Use for_each_intel_connector_iter(). (Jani)

Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250428134716.3396802-2-imre.deak@intel.com