drm/i915/pps: pass intel_dp to pps_name()

Currently all of intel_pps.c passes struct intel_dp around. Do the same
with pps_name() instead of passing both struct drm_i915_private and
struct intel_pps.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/f2a7fec4a2ff1f09cb73e6734604fae99ab6b11a.1725012870.git.jani.nikula@intel.com