drm/i915/pps: rename intel_dp_init_panel_power_sequencer* functions

There are a number of functions that "init" pps in various ways. Try to
find some more consistency in the naming.

Rename:
 - intel_dp_init_panel_power_sequencer -> pps_init_delays
 - intel_dp_init_panel_power_sequencer_registers -> pps_init_registers
 - intel_dp_init_panel_power_timestamps -> pps_init_timestamps

as this is what the functions do. Skip the intel_ prefix here to
emphasize these are static and not exported.

No functional changes.

Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/15260c28060f3f90276ab395da4d3999ccdb641f.1610127741.git.jani.nikula@intel.com