drm/i915/pps: Split pps_init_delays() into distinct parts

[ Upstream commit 75bd0d5e

 ]

Split each of the hw/vbt/spec PPS delay initialization into
separate functions to make the whole thing less cluttered.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220510104242.6099-4-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Stable-dep-of: 607f4176

 ("drm/i915/dsi: filter invalid backlight and CABC ports")
Signed-off-by: Sasha Levin <sashal@kernel.org>